[build] Use $(shell ...) to invoke BUILD_ID_CMD

When using $(shell), make will first invoke BUILD_ID_CMD and then have
the value defined when calling $(LD).  This means we get to see the
_build_id when building with make V=1.  Previously the build_id was
figured out as a subshell command run during the recipe execution
without being able to see the build_id itself.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
1 file changed
tree: 70dfdbef328cab58225b1dd843715eb794326e60
  1. contrib/
  2. src/
  3. .travis.yml
  4. COPYING
  5. COPYING.GPLv2
  6. COPYING.UBDL
  7. README