build: Fix build and tests on macOS

This commit addresses several compatibility issues that prevented Wayland
from building and passing its test suite on macOS

Core and Compatibility changes:
- Emulate Linux behavior by explicitly setting O_NONBLOCK on connections
  (fixes blocking sendmsg issues on macOS).
- Fix compilation on platforms missing SOCK_CLOEXEC and MSG_CMSG_CLOEXEC.
- Implement wl_os_socket_peercred() using LOCAL_PEERPID for macOS.
- Ensure availability of struct itimerspec (required for POSIX Timers API).

Test suite fixes:
- Add socketpair_cloexec() wrapper to handle platforms without atomic
  SOCK_CLOEXEC support.
- Add implementation of memrchr() for platforms that do not provide it.
- Implement is_debugger_attached() for macOS to handle test timeouts.
- Fix tests to handle Mach-O binary format (instead of ELF).
- Update egl-symbols-check to support macOS *.dylib Mach-O libraries.

Build system:
- Add meson option 'xml_catalog' to allow specifying custom catalog paths.

Signed-off-by: Martin Lopatář <lopin@dataplex.cz>

tests/test-runner.h

@@ -37,11 +37,17 @@ struct test {
 	int must_fail;
 } __attribute__ ((aligned (16)));
 
+#ifdef __APPLE__
+#define TEST_SECTION "__DATA,test_section"
+#else
+#define TEST_SECTION "test_section"
+#endif
+
 #define TEST(name)							\
 	static void name(void);						\
 									\
 	const struct test test##name					\
-		 __attribute__ ((used, section ("test_section"))) = {	\
+		 __attribute__ ((used, section (TEST_SECTION))) = {	\
 		#name, name, 0						\
 	};								\
 									\
@@ -51,7 +57,7 @@ struct test {
 	static void name(void);						\
 									\
 	const struct test test##name					\
-		 __attribute__ ((used, section ("test_section"))) = {	\
+		 __attribute__ ((used, section (TEST_SECTION))) = {	\
 		#name, name, 1						\
 	};								\
 									\
@@ -86,6 +92,9 @@ test_sleep(unsigned int);
 void
 test_disable_coredumps(void);
 
+int
+socketpair_cloexec(int domain, int type, int protocol, int sv[2]);
+
 #define DISABLE_LEAK_CHECKS				\
 	do {						\
 		extern int fd_leak_check_enabled;	\