Use the build.pl parallelism again.

Makefile.in

@@ -7,7 +7,6 @@ SHELL=/usr/bin/env bash
 define forward_to_gbuild
 @GNUMAKE@ -f $(dir $(realpath $(firstword $(MAKEFILE_LIST))))/GNUmakefile.mk \
 	$(if @VERBOSE@,,-s) \
-	--jobs="@GMAKE_PARALLELISM@" \
 	$(1)
 endef
 

set_soenv.in

@@ -1771,6 +1771,7 @@ else
    ToFile( "SOLARLIB_FOR_BUILD", $SOLARLIB,      "e" );
    ToFile( "WORKDIR_FOR_BUILD", $WORKDIR,        "e" );
 }
+ToFile( "BUILD_NCPUS",          "@BUILD_NCPUS@", "e" );
 ToFile( "GMAKE_PARALLELISM",    "@GMAKE_PARALLELISM@", "e" );
 ToFile( "GMAKE_MODULE_PARALLELISM","@GMAKE_MODULE_PARALLELISM@", "e" );
 ToFile( "SIZEOF_SHORT",         "@SIZEOF_SHORT@", "e" );

solenv/gbuild/extensions/post_BuildplTargets.mk

@@ -50,7 +50,7 @@ gb_MAKETARGET=all
 endif
 
 define gb_BuildplTarget_command
-cd $(SRCDIR)/$(1) && unset MAKEFLAGS && $(SOLARENV)/bin/build.pl --all gb_MAKETARGET=$(gb_MAKETARGET)
+cd $(SRCDIR)/$(1) && unset MAKEFLAGS && $(SOLARENV)/bin/build.pl -P$(BUILD_NCPUS) --all -P$(GMAKE_PARALLELISM) gb_MAKETARGET=$(gb_MAKETARGET)
 endef
 
 .PHONY: smoketestoo_native instsetoo_native cross-build-toolset dev-install all build