Enable verbose build. By default gdb ignores even --disable-silent-rules.
Override verbosity back to non-silent.

https://bugs.gentoo.org/695936
--- a/gdb/silent-rules.mk
+++ b/gdb/silent-rules.mk
@@ -1,5 +1,4 @@
-# If V is undefined or V=0 is specified, use the silent/verbose/compact mode.
-V ?= 0
+V ?= 1
 ifeq ($(V),0)
 ECHO_CXX =    @echo "  CXX    $@";
 ECHO_CXXLD =  @echo "  CXXLD  $@";