ci: Add CI build for macOS

Note that this skips the 'make distcheck' stage due to two reasons:

  * GitHub considers macOS cpu cycles to be very expensive, and
    distcheck basically doubles the build cycles
  * For reasons yet unknown, 'make distcheck' on macOS fails with
    the compiler being unable to create an executable.

.github/workflows/ccpp.yml

@@ -26,31 +26,54 @@ jobs:
     name: '${{ matrix.os }}'
 
     strategy:
+      fail-fast: true
       matrix:
-        os: [ubuntu-latest]
+        os: [ubuntu-latest, macos-latest]
 
     steps:
       - uses: actions/checkout@v3
 
-      - name: 'Determine number of cores to build on'
+      - name: 'Determine number of cores to build on (Linux)'
+        if: runner.os == 'Linux'
         run: echo NPROC=$(nproc) >> $GITHUB_ENV
 
+      - name: 'Determine number of cores to build on (macOS)'
+        if: runner.os == 'macOS'
+        run: echo NPROC=$(sysctl -n hw.logicalcpu) >> $GITHUB_ENV
+
       # Setting MAKE interferes with Makefile{,.in,.am} using $(MAKE) internally
       - name: 'Prepare concurrent make'
         run: if test "x$NPROC" = x; then echo ci_MAKE="make" >> $GITHUB_ENV; echo "NPROC must be set"; exit 1; else echo ci_MAKE="make -j${NPROC} -l${NPROC}" >> $GITHUB_ENV; fi
 
-      - name: 'Update software database'
+      - name: 'Update software database (Linux)'
+        if: runner.os == 'Linux'
         run: sudo apt-get update
 
-      - name: 'Work around apt-get 3rd party repo libgd-dev dependency'
+      - name: 'Update software database (macOS)'
+        if: runner.os == 'macOS'
+        run: brew update
+
+      - name: 'Work around apt-get 3rd party repo libgd-dev dependency (Linux)'
+        if: runner.os == 'Linux'
         run: sudo apt-get remove nginx libgd3
 
-      - name: 'Install build requirements'
+      - name: 'Install build requirements (Linux)'
+        if: runner.os == 'Linux'
         run: sudo apt-get install -y autopoint gettext libusb-1.0-0-dev libcurl4-openssl-dev libgd-dev
 
-      - name: 'OS specific build flags'
+      - name: 'Install build requirements (macOS)'
+        if: runner.os == 'macOS'
+        run: brew install automake gd gettext libexif libtool libusb
+
+      - name: 'OS specific build flags (Linux)'
+        if: runner.os == 'Linux'
         run: echo OS_SPECIFIC_CPPFLAGS="" >> $GITHUB_ENV
 
+      # FIXME: Fix source to build without the -D_DARWIN_C_SOURCE here
+      - name: 'OS specific build flags (macOS)'
+        if: runner.os == 'macOS'
+        run: echo OS_SPECIFIC_CPPFLAGS="-D_DARWIN_C_SOURCE -I$(brew --prefix)/include" >> $GITHUB_ENV
+
       - name: 'autoreconf'
         run: autoreconf -i -f
 
@@ -63,7 +86,9 @@ jobs:
       - name: 'make check'
         run: set -x; ${ci_MAKE} CPPFLAGS="${OS_SPECIFIC_CPPFLAGS}" check
 
-      - name: 'make distcheck'
+      # FIXME: fix make distcheck to run on macOS
+      - name: 'make distcheck (non-macOS)'
+        if: runner.os != 'macOS'
         run: set -x; ${ci_MAKE} CPPFLAGS="${OS_SPECIFIC_CPPFLAGS}" DISTCHECK_CONFIGURE_FLAGS="${COMMON_CONFIGURE_FLAGS}" distcheck
 
       - name: 'make install'
@@ -72,6 +97,14 @@ jobs:
       - name: 'make installcheck'
         run: set -x; ${ci_MAKE} CPPFLAGS="${OS_SPECIFIC_CPPFLAGS}" installcheck
 
+      - name: 'find ldd replacement (MacOS)'
+        if: runner.os == 'macOS'
+        run: echo 'LDD=otool -L' >> $GITHUB_ENV
+
+      - name: 'find ldd replacement (Linux)'
+        if: runner.os == 'Linux'
+        run: echo 'LDD=ldd' >> $GITHUB_ENV
+
       - name: 'Build and run example libgphoto2 frontend (ambs-lgp2-frontend)'
         run: |
           set -x
@@ -83,8 +116,8 @@ jobs:
           autoreconf -vis
           ./configure --prefix="$PWD/__pref"
           make
-          ldd ambs-lgp2-frontend
+          ${LDD-false} ambs-lgp2-frontend
           ./ambs-lgp2-frontend
           make install
-          ldd __pref/bin/ambs-lgp2-frontend
+          ${LDD-false} __pref/bin/ambs-lgp2-frontend
           __pref/bin/ambs-lgp2-frontend