devel/cmake-core: Fix build with libnghttp2 installed

While building the bundled curl, -I/usr/local/include appears too early
on the compiler command line causing the compiler to use headers from
an installed libnghttp2 instead of the bundled libnghttp2.  Add
USES=localbase so CFLAGS contains -isystem /usr/local/include making
the compiler search the directory after all the -I flags.

PR:		269253

devel/cmake-core/Makefile

@@ -16,7 +16,7 @@ LIB_DEPENDS=	libexpat.so:textproc/expat2 \
 		libuv.so:devel/libuv \
 		librhash.so:security/rhash
 
-USES=		cmake:_internal compiler:c++11-lang cpe ncurses ssl
+USES=		cmake:_internal compiler:c++11-lang cpe localbase ncurses ssl
 
 CPE_VENDOR=	cmake_project
 HAS_CONFIGURE=	yes