On systems where cc != gcc, compilation likely fails because we are
using quite some gccisms in osl. So default to gcc but let the user
override the default by setting CC manually.
The straight-forward CC ?= gcc does not work with gnu make as make
assigns CC the default value "cc".
Thanks to Steffen Schmidt for pointing out this shortcoming.
man_pages := oslfsck.1
INSTALL := install
-CC := gcc
+ifeq "$(origin CC)" "default"
+ CC := gcc
+endif
MKDIR := mkdir -p
RM := rm -f
LN := ln