gcc: put target-specific libs in lib output

Co-authored-by: Matthew Bauer <mjbauer95@gmail.com>

pkgs/development/compilers/gcc/builder.sh

@@ -213,9 +213,24 @@ preInstall() {
 
 postInstall() {
     # Move runtime libraries to $lib.
-    moveToOutput "lib/lib*.so*" "$lib"
-    moveToOutput "lib/lib*.la"  "$lib"
-    moveToOutput "lib/lib*.dylib" "$lib"
+    if [[ -n "$targetConfig" && -d "$out/$targetConfig/lib" && -n "$(ls -A $out/$targetConfig/lib)" ]]; then
+        moveToOutput "$targetConfig/lib/lib*.so*" "$lib"
+        moveToOutput "$targetConfig/lib/lib*.la" "$lib"
+        moveToOutput "$targetConfig/lib/lib*.dylib" "$lib"
+        mv "$lib/$targetConfig"/lib/* "$lib/lib/"
+        rmdir -p --ignore-fail-on-non-empty "$lib/$targetConfig/lib" || :
+    elif [[ -n "$targetConfig" && -d "$out/$targetConfig/lib64" && -n "$(ls -A $out/$targetConfig/lib64)" ]]; then
+        moveToOutput "$targetConfig/lib64/lib*.so*" "$lib"
+        moveToOutput "$targetConfig/lib64/lib*.la" "$lib"
+        moveToOutput "$targetConfig/lib64/lib*.dylib" "$lib"
+        mv "$lib/$targetConfig"/lib64/* "$lib/lib/"
+        rmdir -p --ignore-fail-on-non-empty "$lib/$targetConfig/lib64" || :
+    else
+        moveToOutput "lib/lib*.so*" "$lib"
+        moveToOutput "lib/lib*.la"  "$lib"
+        moveToOutput "lib/lib*.dylib" "$lib"
+    fi
+
     moveToOutput "share/gcc-*/python" "$lib"
 
     for i in "$lib"/lib/*.{la,py}; do