[PATCH, libgfortran] Remove AM_MAKEFLAGS.

[David Edelsohn]

	This looks like a shell substitution problem.  Top-level Makefile
EXTRA_TARGET_FLAGS specifically replaces CC with CC_FOR_TARGET, but does
not expand immediately:

# Flags to pass down to makes which are built with the target environment.
# The double $ decreases the length of the command line; the variables
# are set in BASE_FLAGS_TO_PASS, and the sub-make will expand them.
...
        'CC=$$(CC_FOR_TARGET)' \

CC_FOR_TARGET already is passed; AM_MAKEFLAGS did not change that.  The
addition of AM_MAKEFLAGS probably forced an extra shell substitution when
all of those variables were passed on the commandline.

David