tools/resolve_btfids: fix build with musl libc

Include the header that defines u32.
This fixes build of 6.6.23 and 6.1.83 kernels for Alpine Linux, which
uses musl libc. I assume that GNU libc indirecly pulls in linux/types.h.

Fixes: 9707ac4fe2f5 ("tools/resolve_btfids: Refactor set sorting with types from btf_ids.h")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218647
Cc: [e-mail]
Signed-off-by: Natanael Copa <[e-mail]>
Tested-by: Greg Thelen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/include/linux/btf_ids.h

···
 #ifndef _LINUX_BTF_IDS_H
 #define _LINUX_BTF_IDS_H
 
+#include <linux/types.h> /* for u32 */
+
 struct btf_id_set {
 	u32 cnt;
 	u32 ids[];