Makefile.inc: Add build targets for IASL & Clang

- Add specific build targets for IASL & CLANG and help for those targets
- Consolidate tool target .PHONY entries

Change-Id: If2960d75310495d9e486b3a08808463a2ff0c644
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12541
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
2 files changed