gdb: use compiled_regex instead of std::regex

gdb: use compiled_regex instead of std::regex

In GDB we should be using compiled_regex instead of std::regex.
Replace one use in producer.c.

There should be no user visible changes after this commit.

gdb/ChangeLog:

	* producer.c: Replace 'regex' include with 'gdb_regex.h'.
	(producer_is_icc): Replace use of std::regex with gdb's
	compiled_regex.