Add option UNIFIED_OBJDIR, on by default, which moves the default build OBJDIR.

This changes the build OBJDIR from the older style of /usr/obj/<srcdir> for
native builds, and /usr/obj/<target>.<target_arch>/<srcdir> for cross builds to
a new simpler format of /usr/obj/<srcdir>/<target>.<target_arch>.  This
new format is used regardless of cross or native build.  It allows
easier management of multiple source tree object directories.

The UNIFIED_OBJDIR option will be removed and its feature made permanent
for the 12.0 release.

Relnotes:	yes (don't note UNIFIED_OBJDIR option since it will be removed)
Prior work:	D3711 D874
Reviewed by:	gjb, sjg
Discussed at:	https://lists.freebsd.org/pipermail/freebsd-arch/2016-May/017805.html
Discussed with:	emaste
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D12840

1 files changed, 12 insertions, 0 deletions

diff --git a/tools/build/options/WITH_UNIFIED_OBJDIR b/tools/build/options/WITH_UNIFIED_OBJDIR
new file mode 100644
index 000000000000..6efc01d09c5e
--- /dev/null
+++ b/tools/build/options/WITH_UNIFIED_OBJDIR
@@ -0,0 +1,12 @@
+.\" $FreeBSD$
+Set to use the unified object directory format for
+.Xr build 7
+targets.
+For cross-builds, native-builds, and sub-directory builds, the format of
+.Pa ${MAKEOBJDIRPREFIX}/${.CURDIR}/${TARGET}.${TARGET_ARCH}
+is used.
+.Pp
+This option is transitional and will be removed before the 12.0 release,
+at which time
+.va WITH_UNIFIED_OBJDIR
+will be enabled permanently.