vlc-debian-win32: Harmonize with -win64 image

vlc-debian-win32/Dockerfile

@@ -12,8 +12,8 @@ ARG CORES=8
 ENV IMAGE_DATE=202211290000
 
 ENV TARGET_TUPLE=i686-w64-mingw32
-ENV TOOLCHAIN_PREFIX=/opt/gcc-$TARGET_TUPLE
-ENV MINGW_PREFIX=$TOOLCHAIN_PREFIX/$TARGET_TUPLE
+ENV TOOLCHAIN_PREFIX=/opt/gcc-${TARGET_TUPLE}
+ENV MINGW_PREFIX=$TOOLCHAIN_PREFIX/${TARGET_TUPLE}
 ENV PATH=$TOOLCHAIN_PREFIX/bin:/opt/protobuf/bin:$PATH
 
 # The wine SDK path differs from version to version, starting from the one in buster, it's