build: cross compile the macOS x86_64 target natively on Apple Silicon

.github/actions/build-macos-x86_64/action.yml

@@ -52,28 +52,42 @@ runs:
         key: maven-${{ inputs.platform-name }}-${{ hashFiles('**/pom.xml') }}
         restore-keys: maven-${{ inputs.platform-name }}-
 
-    - name: Set up JDK
+    # The runner is Apple Silicon. The build runs natively and cross compiles
+    # for Intel; only the tests need an Intel JVM, to load what was built, and
+    # that one runs under Rosetta.
+    - id: jdk-x64
+      name: Set up JDK (x64, for the tests)
       uses: actions/setup-java@v5
       with:
         architecture: 'x64'
         java-version: ${{ inputs.java-version }}
         distribution: 'temurin'
+        overwrite-settings: false
+
+    # Set up last, so that it is the JAVA_HOME the build runs with and the one
+    # whose settings.xml carries the deploy credentials.
+    - name: Set up JDK (arm64, for the build)
+      uses: actions/setup-java@v5
+      with:
+        architecture: 'aarch64'
+        java-version: ${{ inputs.java-version }}
+        distribution: 'temurin'
         server-id: central
         server-username: MAVEN_USERNAME
         server-password: MAVEN_TOKEN
 
     - name: Build
-      run: arch -x86_64 mvn package -DskipTests -Pmacos-cross-x86_64
+      run: mvn package -DskipTests -Pmacos-cross-x86_64
       shell: bash
 
     - name: Test
-      run: arch -x86_64 mvn -B jar:jar surefire:test -Pmacos-cross-x86_64
+      run: JAVA_HOME="${{ steps.jdk-x64.outputs.path }}" mvn -B jar:jar surefire:test -Pmacos-cross-x86_64
       shell: bash
 
     - name: Deploy
       if: ${{ github.event_name != 'pull_request' && github.repository == 'devopvoid/webrtc-java' }}
       env:
         MAVEN_USERNAME: ${{ inputs.maven-username }}
         MAVEN_TOKEN: ${{ inputs.maven-password }}
-      run: arch -x86_64 mvn deploy -DskipTests -Pmacos-cross-x86_64
+      run: mvn deploy -DskipTests -Pmacos-cross-x86_64
       shell: bash

.github/actions/release-macos-x86_64/action.yml

@@ -44,19 +44,31 @@ runs:
         key: maven-${{ inputs.platform-name }}-${{ hashFiles('**/pom.xml') }}
         restore-keys: maven-${{ inputs.platform-name }}-
 
-    - name: Set up JDK ${{ inputs.java-version }}
+    # The runner is Apple Silicon. The build runs natively and cross compiles
+    # for Intel; only the tests need an Intel JVM, to load what was built, and
+    # that one runs under Rosetta.
+    - id: jdk-x64
+      name: Set up JDK ${{ inputs.java-version }} (x64, for the tests)
       uses: actions/setup-java@v5
       with:
         architecture: 'x64'
         java-version: ${{ inputs.java-version }}
         distribution: 'temurin'
 
+    # Set up last, so that it is the JAVA_HOME the build runs with.
+    - name: Set up JDK ${{ inputs.java-version }} (arm64, for the build)
+      uses: actions/setup-java@v5
+      with:
+        architecture: 'aarch64'
+        java-version: ${{ inputs.java-version }}
+        distribution: 'temurin'
+
     - name: Build
-      run: arch -x86_64 mvn package -DskipTests -Pmacos-cross-x86_64
+      run: mvn package -DskipTests -Pmacos-cross-x86_64
       shell: bash
 
     - name: Test
-      run: arch -x86_64 mvn -B jar:jar surefire:test -Pmacos-cross-x86_64
+      run: JAVA_HOME="${{ steps.jdk-x64.outputs.path }}" mvn -B jar:jar surefire:test -Pmacos-cross-x86_64
       shell: bash
 
     # Maven Central publishes a version as one atomic bundle, so this job must not

pom.xml

@@ -355,6 +355,16 @@
 				<platform.module>webrtc.macos.aarch64</platform.module>
 			</properties>
 		</profile>
+		<!-- Builds for Intel Macs on an Apple Silicon one. The macos-aarch64
+		     profile above is still activated there by the host, so this one has
+		     to be declared after it for its properties to win. -->
+		<profile>
+			<id>macos-cross-x86_64</id>
+			<properties>
+				<platform.classifier>macos-x86_64</platform.classifier>
+				<platform.module>webrtc.macos.x86_64</platform.module>
+			</properties>
+		</profile>
 	</profiles>
 
 	<dependencies>

webrtc-java-media/pom.xml

@@ -42,8 +42,8 @@
 		     same glibc floor. On Linux that also means compiling with
 		     -nostdinc++ and taking the C++ standard library from where
 		     webrtc-jni takes it, which is what webrtc.install.dir is for
-		     below. macOS builds for the architecture Maven runs as and needs
-		     no file. -->
+		     below. A native macOS build needs no file; the Intel build made on
+		     Apple Silicon takes webrtc-jni's cross one. -->
 		<cmake.toolchain.file />
 		<jni.toolchain.dir>${project.basedir}/../webrtc-jni/src/main/cpp/toolchain</jni.toolchain.dir>
 		<!-- Where webrtc-jni installed WebRTC, and with it the libc++ that its
@@ -250,12 +250,15 @@
 					<arch>aarch64</arch>
 				</os>
 			</activation>
-			<!-- Both macOS targets build for the architecture Maven itself is
-			     running as, the Intel one under "arch -x86_64", so neither is a
-			     cross build and neither needs a toolchain file. -->
+			<!-- Builds for the architecture Maven itself is running as, so it
+			     needs no toolchain file. -->
 		</profile>
+		<!-- The Intel build, made on an Apple Silicon host. -->
 		<profile>
 			<id>macos-cross-x86_64</id>
+			<properties>
+				<cmake.toolchain.file>${jni.toolchain.dir}/x86_64-macos-cross.cmake</cmake.toolchain.file>
+			</properties>
 		</profile>
 
 		<!-- Reruns the tests under -Xcheck:jni, which turns a JNI reference

webrtc-java-media/src/main/cpp/dependencies/ffmpeg/CMakeLists.txt

@@ -383,8 +383,11 @@ else()
         # make install strips what it installs, with whichever strip is on
         # the PATH, and the host's cannot read a binary built for another
         # architecture: "unable to recognise the format of the input file".
-        # Shipping unstripped costs a little size and nothing else.
-        list(APPEND FFMPEG_CONFIGURE_ARGS --disable-stripping)
+        # Shipping unstripped costs a little size and nothing else. Apple's
+        # strip reads Mach-O of every architecture, so there it stays on.
+        if(NOT APPLE)
+            list(APPEND FFMPEG_CONFIGURE_ARGS --disable-stripping)
+        endif()
 
         # An assembler for a foreign architecture is a build prerequisite of
         # its own, and this module is not fast enough to need one yet.