gcc: fix multilib build

Fixes #8706, thanks to @cpages a lot.
Also ported to gcc5, without testing that one yet.

Changed files
+2 -2
pkgs
development
compilers
+1 -1
pkgs/development/compilers/gcc/4.9/default.nix
···
" --with-gnu-as --without-gnu-ld "
else ""}
--enable-lto
-
${if enableMultilib then "--disable-libquadmath" else "--disable-multilib"}
+
${if enableMultilib then "--enable-multilib --disable-libquadmath" else "--disable-multilib"}
${if enableShared then "" else "--disable-shared"}
${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
${optionalString (isl != null) "--with-isl=${isl}"}
+1 -1
pkgs/development/compilers/gcc/5/default.nix
···
" --with-gnu-as --without-gnu-ld "
else ""}
--enable-lto
-
${if enableMultilib then "--disable-libquadmath" else "--disable-multilib"}
+
${if enableMultilib then "--enable-multilib --disable-libquadmath" else "--disable-multilib"}
${if enableShared then "" else "--disable-shared"}
${if enablePlugin then "--enable-plugin" else "--disable-plugin"}
${optionalString (isl != null) "--with-isl=${isl}"}