tools/nolibc: move exported functions to their own section

Some functions like raise() and memcpy() are permanently exported because
they're needed by libgcc on certain platforms. However most of the time
they are not needed and needlessly take space.

Let's move them to their own sub-section, called .text.nolibc_<function>.
This allows ld to get rid of them if unused when passed --gc-sections.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/stdlib.h

@@ -314,7 +314,7 @@ int msleep(unsigned int msecs)
 }
 
 /* This one is not marked static as it's needed by libgcc for divide by zero */
-__attribute__((weak,unused))
+__attribute__((weak,unused,section(".text.nolibc_raise")))
 int raise(int signal)
 {
 	return sys_kill(sys_getpid(), signal);

tools/include/nolibc/string.h

@@ -69,7 +69,7 @@ void *memmove(void *dst, const void *src, size_t len)
 }
 
 /* must be exported, as it's used by libgcc on ARM */
-__attribute__((weak,unused))
+__attribute__((weak,unused,section(".text.nolibc_memcpy")))
 void *memcpy(void *dst, const void *src, size_t len)
 {
 	return _nolibc_memcpy_up(dst, src, len);