toolchain/gcc: parallelize make install

If the staging dir was deleted, the build needs to recompile some files.
This change speeds up this corner case significantly

Signed-off-by: Felix Fietkau <nbd@nbd.name>

toolchain/gcc/final/Makefile

@@ -67,7 +67,7 @@ endef
 
 define Host/Install
 	$(CleanupToolchain)
-	$(_SINGLE)$(GCC_MAKE) -C $(GCC_BUILD_DIR) install
+	+$(GCC_MAKE) $(HOST_JOBS) -C $(GCC_BUILD_DIR) install
 	# Set up the symlinks to enable lying about target name.
 	set -e; \
 	(cd $(TOOLCHAIN_DIR); \

toolchain/gcc/initial/Makefile

@@ -18,7 +18,7 @@ define Host/Compile
 endef
 
 define Host/Install
-	$(GCC_MAKE) -C $(GCC_BUILD_DIR) \
+	+$(GCC_MAKE) $(HOST_JOBS) -C $(GCC_BUILD_DIR) \
 		prefix="$(TOOLCHAIN_DIR)/initial" \
 		install-gcc \
 		install-target-libgcc