pmb.aportgen.gcc: set libgcc=false (MR 2203)

Do not build the foreign arch libgcc. We are using the one provided by
Alpine's binary repository instead, and when building it here and trying
to use it, we actually run into a conflict.

I tried setting BOOTSTRAP="nolibc" first since there is already logic to
then disable libgcc in the APKBUILD. But that also disables g++ which we
do want to build, so we can't use this.

Fixes: issue 2168

pmb/aportgen/gcc.py

@@ -78,6 +78,9 @@ def generate(args, pkgname):
         # use CBUILDROOT as sysroot. In the original APKBUILD this is a local
         # variable, but we make it a global one.
         '*_cross_configure=*': None,
+
+        # Do not build foreign arch libgcc, we use the one from Alpine (#2168)
+        '_libgcc=true*': '_libgcc=false',
     }
 
     pmb.aportgen.core.rewrite(args, pkgname, based_on, fields,

test/testdata/aportgen/pmaports/cross/gcc-armhf/APKBUILD

@@ -53,7 +53,7 @@ replaces="libstdc++ binutils"
 : "${LANG_JIT:=true}"
 
 _libgomp=true
-_libgcc=true
+_libgcc=false
 _libatomic=true
 _libitm=true