Move some things from config.sh to ext_config.sh

scripts/config.sh

@@ -18,10 +18,5 @@ export RUSTC=$dir"/bin/cg_clif"
 export RUSTDOCFLAGS=$linker' -Cpanic=abort -Zpanic-abort-tests '\
 '-Zcodegen-backend='$dir'/lib/'$dylib' --sysroot '$dir
 
-# FIXME fix `#[linkage = "extern_weak"]` without this
-if [[ "$(uname)" == 'Darwin' ]]; then
-   export RUSTFLAGS="$RUSTFLAGS -Clink-arg=-undefined -Clink-arg=dynamic_lookup"
-fi
-
 export LD_LIBRARY_PATH="$(rustc --print sysroot)/lib:"$dir"/lib"
 export DYLD_LIBRARY_PATH=$LD_LIBRARY_PATH

scripts/ext_config.sh

@@ -25,3 +25,8 @@ if [[ "$HOST_TRIPLE" != "$TARGET_TRIPLE" ]]; then
       echo "Unknown non-native platform"
    fi
 fi
+
+# FIXME fix `#[linkage = "extern_weak"]` without this
+if [[ "$(uname)" == 'Darwin' ]]; then
+   export RUSTFLAGS="$RUSTFLAGS -Clink-arg=-undefined -Clink-arg=dynamic_lookup"
+fi