WITH_META_MODE: Lessen the filemon(4) requirement scope.

- Move the sys.mk filemon requirement to bsd.init.mk as a warning.
  This is intended only to show when building directly in a subdirectory
  without filemon loaded.
- Move the error into Makefile and only apply it when building
  from the META_TGT_WHITELIST target list.

-DNO_FILEMON can be used to suppress both the warning and the error but
makes WITH_META_MODE less useful.  It will only compare build commands
in this mode rather than track all dependencies.

This fixes installing from a jail which doesn't need filemon in this
phase [1].

Reported by:	Nikolai Lifanov <lifanov@mail.lifanov.com> [1]
Approved by:	re (implicit)
Sponsored by:	EMC / Isilon Storage Division

1 files changed, 6 insertions, 2 deletions

diff --git a/tools/build/options/WITH_META_MODE b/tools/build/options/WITH_META_MODE
index 775ab01..65595ac 100644
--- a/tools/build/options/WITH_META_MODE
+++ b/tools/build/options/WITH_META_MODE
@@ -7,9 +7,13 @@ using
 The meta file is created in the OBJDIR as
 .Pa target.meta .
 These meta files track the command ran, its output, and the current directory.
-When the
+The
 .Xr filemon 4
-module is loaded, any files used by the commands executed will be tracked as
+module is required unless
+.Va NO_FILEMON
+is defined.
+When the module is loaded, any files used by the commands executed will be
+tracked as
 dependencies for the target in its meta file.
 The target will be considered out-of-date and rebuilt if any of the following
 are true compared to the last build: