Disable parallel gcc builds in GitHub Actions

.github/workflows/sgdk-docker.yml

@@ -61,6 +61,9 @@ jobs:
           file: deps/gcc.Dockerfile
           context: deps/
           platforms: linux/amd64,linux/arm64
+          # Disable parallel builds, which are hanging in GitHub Actions.
+          build-args: |
+            PARALLEL_BUILD=0
           tags: ghcr.io/${{ github.actor }}/sgdk-m68k-gcc:latest
           push: ${{ github.event_name == 'push' }}
 

deps/gcc.Dockerfile

@@ -10,6 +10,7 @@ ARG _mpfrver=4.1.0
 ARG _mpcver=1.2.1
 ARG _gmpver=6.2.1
 ARG _newlib_ver=4.1.0
+ARG PARALLEL_BUILD=1
 
 ENV TARGET=m68k-elf
 ENV TARGET_CPU=m68000
@@ -26,6 +27,7 @@ ENV SRCDIR="$BASEDIR/src"
 ENV BUILDDIR="$BASEDIR/build"
 ENV INSTALLDIR="$BASEDIR/install"
 ENV STAGINGDIR="$BASEDIR/staging"
+ENV PARALLEL_BUILD="$PARALLEL_BUILD"
 
 RUN mkdir -p "$SRCDIR"
 RUN mkdir -p "$BUILDDIR"
@@ -42,6 +44,13 @@ RUN wget ftp://sourceware.org/pub/newlib/${NEWLIB}.tar.gz  -O - | tar -xz
 
 RUN apk add --no-cache bash build-base zlib-dev
 
+# Choose parallel build or not.  Parallel builds are hanging under qemu on
+# GitHub, so we serialize building there.  If parallel builds are disabled,
+# replace nproc so it always says "1".
+RUN echo "nproc = $(nproc)"
+RUN echo "PARALLEL_BUILD = $PARALLEL_BUILD"
+RUN if [[ "$PARALLEL_BUILD" == 0 ]]; then echo -e "#!/bin/sh\necho 1" > $(which nproc); fi
+
 #################################################################################
 ##########################    Building binutils    ##############################
 #################################################################################
@@ -134,7 +143,7 @@ RUN rm "$INSTALLDIR/$GCC/usr/lib/libcc1.so.0.0.0"
 RUN cp -ar "$INSTALLDIR/$GCC/usr/" "$STAGINGDIR"
 
 
-# Second stage, just  copy the built files
+# Second stage, just copy the built files
 FROM scratch
 ARG BASEDIR
 WORKDIR /m68k