tests: remove accidentally committed Linux test binaries + gitignore them — fixes make test-c on non-Linux (#226)

c/tests/test_schema_gbnf and c/tests/test_compat_direct were committed
as Linux x86-64 ELF executables (slipped in via #111). On any other
platform make test-c considers them up to date and execs them, failing
with OSError: [Errno 8] Exec format error. Remove them and add the two
names to .gitignore alongside the other test binaries already listed,
so each platform rebuilds its own.

.gitignore

@@ -31,6 +31,10 @@ c/tests/test_tier
 c/tests/test_tier.exe
 c/tests/test_grammar
 c/tests/test_grammar.exe
+c/tests/test_schema_gbnf
+c/tests/test_schema_gbnf.exe
+c/tests/test_compat_direct
+c/tests/test_compat_direct.exe
 
 # oracoli tiny generati (make_glm_oracle.py) e dati benchmark scaricati
 c/glm_tiny/