build: support cross-compiling directly from git checkout

build: support cross-compiling directly from git checkout

* src/local.mk: Compile the make-prime-list in a temporary directory
using $(BUILD_CC) so it can be run even when $(CC) is a cross-compiler.
Add some comments.
(noinst_PROGRAMS): Remove src/make-prime-list.
(src_make_prime_list_LDADD): Remove variable.
* src/make-prime-list.c: Don't include config.h and attributes.h.
Remove unnecessary #undefs
(ATTRIBUTE_CONST, ATTRIBUTE_MALLOC): Define for the host compiler.
Fixes https://bugs.gnu.org/78377