Add -static earlier to LDFLAGS for compile_prog()

Add -static to LDFLAGS earlier as to run the compile_prog() tests with
this flags, this will avoid turning on features for which a shared
library is available but not a static one.

Signed-off-by: Loïc Minier <lool@dooz.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>