What is the OPTION in the GCC's option "-Wl,OPTION"?

The linker is called ld. Googling for ld options gives e.g. http://sourceware.org/binutils/docs-2.16/ld/Options.html

It is linker options written like this (from my makefile):

FLAGS += -Wl,--enable-auto-import,--enable-runtime-pseudo-reloc

The linker options are listed in detail on the linker man page: ld (the GNU linker)

The options are for the ld linker, and are listed here.