build: fix invalid gcc compiler flag error
build: fix invalid gcc compiler flag error

With some gcc versions, the flag -Wno-reserved-id-macros flags doesn't
exist.  This patch adds a test for this flag, before adding it to the
compile line.

Signed-off-by: Keith Holman <8f11bf990f36a0538e23d1881157bace2cc85066@windriver.com>

GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver