* lib/gdb.exp (CFLAGS): Remove, unreferenced.

	* lib/gdb.exp (CFLAGS): Remove, unreferenced.
	(CXXFLAGS): Remove, unreferenced.
	(B_OPTIONS): Add for -B options and add code to initialize with previous
	-B options and also add -B option to pick up cross compiled runtime.
	(TARGET_INCLUDES): Add for -I options and add code to initialize when
	doing cross compiles.
	(target_alias): Declare global.
	(xgcc): Set variable to full path of gcc in build tree.  Use findfile
	to verify that gcc exists in build tree, and if so set CC to that
	gcc and to use B_OPTIONS and TARGET_INCLUDES.