package: build mtd-utils, libsepol and libselinux in parallel

A package builds with -j1 unless it sets PKG_BUILD_PARALLEL, and 171 of
the 220 packages do not set it. These three gain the most from the job
server on a cold build of this tree:

  mtd-utils   24.77 s -> 6.43 s
  libsepol    17.99 s -> 2.18 s
  libselinux   7.82 s -> 1.89 s

mtd-utils runs while nothing else does, so its 18 s count against the
wall clock in full.

Each one builds three times out of three with the job server, and each
build writes a tree that is identical to the one a serial build writes.
nftables gains as well, 17.9 s to 13.0 s, but it is left alone: its
build directory differs between two serial builds, so the check that
covers the other three says nothing about it.

Signed-off-by: John Crispin <john@phrozen.org>

package/libs/libselinux/Makefile

@@ -22,6 +22,8 @@ PKG_BUILD_FLAGS:=no-lto
 
 HOST_BUILD_DEPENDS:=libsepol/host musl-fts/host pcre2/host
 
+PKG_BUILD_PARALLEL:=1
+
 include $(INCLUDE_DIR)/package.mk
 include $(INCLUDE_DIR)/host-build.mk
 

package/libs/libsepol/Makefile

@@ -18,6 +18,8 @@ PKG_CPE_ID:=cpe:/a:selinuxproject:libsepol
 
 PKG_BUILD_FLAGS:=no-lto
 
+PKG_BUILD_PARALLEL:=1
+
 include $(INCLUDE_DIR)/package.mk
 include $(INCLUDE_DIR)/host-build.mk
 

package/utils/mtd-utils/Makefile

@@ -30,6 +30,8 @@ PKG_CPE_ID:=cpe:/a:mtd-utils_project:mtd-utils
 
 PKG_MAINTAINER:=John Crispin <john@phrozen.org>
 
+PKG_BUILD_PARALLEL:=1
+
 include $(INCLUDE_DIR)/package.mk
 
 define Package/mtd-utils/Default