+By default, configure will use the "gcc" compiler if found. You can
+use a different compiler, or add unusual options for compiling or
+linking that the "configure" script does not know about, by giving
+"configure" initial values for these on its command line or in its
+environment. For example,
+
+ ./configure CC=c89 CFLAGS=-O2 LIBS=-lposix
+
+If you wish to add options that are only used at compile time instead of
+link time, you can use the CPPFLAGS variable:
+
+ ./configure CPPFLAGS='-Wextra -Wno-sign-compare'