toolchain/gdb: fix compilation with ccache

For some reason, one of the configure checks results in some infinite
loop and ends up spawning endless gcc processes, causing OOM. Just pass
a configure var to avoid it.

Same fix as 6e23813c1ed7494a9da3b5e59cfcafd71097c420

Signed-off-by: Rosen Penev <[email protected]>

toolchain/gdb/Makefile

@@ -22,6 +22,7 @@ HOST_BUILD_PARALLEL:=1
 include $(INCLUDE_DIR)/toolchain-build.mk
 
 HOST_CONFIGURE_VARS += \
+	acx_cv_cc_gcc_supports_ada=false \
 	gdb_cv_func_sigsetjmp=yes
 
 HOST_CONFIGURE_ARGS = \