Build the sysroot

Author: antoyo

.github/workflows/gcc12.yml

@@ -121,4 +121,4 @@ jobs:
         # TODO(antoyo): add --build-sysroot when the build with libgccjit 12 is fixed.
         # FIXME(antoyo): we need to set GCC_EXEC_PREFIX so that the linker can find the linker plugin.
         # Not sure why it's not found otherwise.
-        GCC_EXEC_PREFIX=/usr/lib/gcc/ ./test.sh --release --clean ${{ matrix.commands }} --no-default-features
+        GCC_EXEC_PREFIX=/usr/lib/gcc/ ./test.sh --release --clean --build-sysroot ${{ matrix.commands }} --no-default-features