Move $(CC) support functions to Kbuild.include so they are available
in the kbuild files.
In addition the following was done:
o as-option documented in Documentation/kbuild/makefiles.txt
o Moved documentation to new section to match
new scope of functions
o added cc-ifversion used to conditionally select a text string
dependent on actual $(CC) version
o documented cc-ifversion
o change so Kbuild.include is read before the kbuild file
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
20a468b513