gdb/testsuite: Add compiler options parameter to function_range helper

gdb/testsuite: Add compiler options parameter to function_range helper

When using the Dejagnu DWARF compiler tests will often use the
function_range helper function to extract the extents of a function.
If the plan is to compiler the file with non-default compiler flags
then we must pass those same compiler flags through to the
function_range helper function.

This will be used in a later commit, there should be no change in the
testsuite behaviour after this commit.

gdb/testsuite/ChangeLog:

	* lib/dwarf.exp (function_range): Allow compiler options to be
	specified.