build-busybox: Disable make, copy mingw32-make.exe as make.exe

The built-in make is a POSIX make tool, which doesn't support
GNU make features.

As we do have GNU make, insert that as "make.exe" in the busybox
directory. Don't do that in the main llvm-mingw bin directory,
which can be used with other environments (e.g. msys2), where the
native make is to be preferred.

Dockerfile.cross

@@ -68,7 +68,10 @@ ARG WITH_BUSYBOX
 
 COPY build-busybox.sh .
 RUN if [ -n "$WITH_BUSYBOX" ]; then \
-        ./build-busybox.sh $CROSS_TOOLCHAIN_PREFIX/busybox --host=$HOST; \
+        ./build-busybox.sh $CROSS_TOOLCHAIN_PREFIX/busybox --host=$HOST && \
+        cp $CROSS_TOOLCHAIN_PREFIX/bin/mingw32-make.exe $CROSS_TOOLCHAIN_PREFIX/busybox/bin/make.exe && \
+        mkdir -p $CROSS_TOOLCHAIN_PREFIX/busybox/share && \
+        cp -a $CROSS_TOOLCHAIN_PREFIX/share/make $CROSS_TOOLCHAIN_PREFIX/busybox/share; \
     fi
 
 ARG TAG

build-busybox.sh

@@ -74,6 +74,7 @@ make mingw64a_defconfig O=$BUILDDIR -j$CORES
 cd $BUILDDIR
 sed -ri 's/^(CONFIG_AR)=y/\1=n/' .config
 sed -ri 's/^(CONFIG_FEATURE_FAIL_IF_UTF8_MANIFEST_UNSUPPORTED)=y/\1=n/' .config
+sed -ri 's/^(CONFIG_MAKE)=y/\1=n/' .config
 $MAKE -j$CORES CROSS_COMPILE=${HOST+$HOST-}
 cp ../LICENSE $PREFIX/LICENSE.txt
 mkdir -p $PREFIX/bin

build-cross-tools.sh

@@ -108,4 +108,9 @@ if [ -z "$NO_MAKE" ]; then
 fi
 if [ -n "$BUSYBOX" ]; then
     ./build-busybox.sh $PREFIX/busybox --host=$HOST
+    if [ -z "$NO_MAKE" ]; then
+        cp $PREFIX/bin/mingw32-make.exe $PREFIX/busybox/bin/make.exe
+        mkdir -p $PREFIX/busybox/share
+        cp -a $PREFIX/share/make $PREFIX/busybox/share
+    fi
 fi