No. Although I didn't manually use the switches with gcc to find
gmp mpc or mpfc. The configure script seemed to me atleast to be
able to find those libraries I put in /usr/local. No when
compiling mpc I believe it was it needed to know where gmp was.
The script needed help there. gmp mpc and mpfc were the only
things gcc to my knowledge needed to compile and run.
There's a difference between configure being able to find the
libraries to link an executable and the dynamic linker being able to
find those libraris to *run* an executable.
If /usr/local/lib is not in your ldconfig cache then it will not
find libgmp.so etc. so you will need to reconfigure ldconfig, or set
LD_LIBRARY_PATH.
Of course since you don't know what the actual error was this is all
just wild speculation. You need to know what the error was and if it
told you to look in config.log, which would have more information.
Try looking in the build directory for $target/libgcc/config.log
which I suspect will show that ld.so couldn't find one of libgmp.so,
libmpfr.so or libmpc.so