meson: disallow Venus debug + LTO build via GCC

What does this MR do and why?

meson: disallow Venus debug + LTO build via GCC

with gcc	optimization	-Db_lto=true
-Dbuildtype=plain	plain (default)	fail
-Dbuildtype=debug	0 (default)	fail
-Dbuildtype=debugoptimized	2 (default)	succeed
-Dbuildtype=release	3 (default)	succeed
-Dbuildtype=minsize	s (default)	succeed
-Dbuildtype=custom	plain	fail
-Dbuildtype=custom	0	fail
-Dbuildtype=custom	g	succeed
-Dbuildtype=custom	1	succeed
-Dbuildtype=custom	2	succeed
-Dbuildtype=custom	3	succeed
-Dbuildtype=custom	s	succeed

Now meson setup prints below:

meson.build:2269:2: ERROR: Problem encountered: With GCC, Venus debug build with LTO enabled is not supported.

Closes: #11006 (closed)

/cc @dh