Fix definitions for Darwin PPC; do not use pthread_setname_np on unsupported OS versions (#1797)

* Correct define for Darwin PPC is __POWERPC__

* util.cpp: do not use pthread_setname_np on unsupported macOS versions

build/cmake_modules/TargetArch.cmake

@@ -61,7 +61,7 @@ set(archdetect_c_code "
     #else
         #error cmake_ARCH mips
     #endif
-#elif defined(__ppc__) || defined(__ppc) || defined(__powerpc__) \\
+#elif defined(__ppc__) || defined(__ppc) || defined(__powerpc__) || defined(__POWERPC__) \\
       || defined(_ARCH_COM) || defined(_ARCH_PWR) || defined(_ARCH_PPC)  \\
       || defined(_M_MPPC) || defined(_M_PPC)
     #if defined(__ppc64__) || defined(__powerpc64__) || defined(__64BIT__)

libi2pd/util.cpp

@@ -22,6 +22,9 @@
 #include <pthread_np.h>
 #endif
 
+#if defined(__APPLE__)
+# include <AvailabilityMacros.h>
+#endif
 
 #ifdef _WIN32
 #include <stdlib.h>
@@ -143,8 +146,15 @@ namespace util
 	}
 
 	void SetThreadName (const char *name) {
-#if defined(__APPLE__) && !defined(__powerpc__)
+#if defined(__APPLE__)
+# if (!defined(MAC_OS_X_VERSION_10_6) || \
+		(MAC_OS_X_VERSION_MAX_ALLOWED < 1060) || \
+		defined(__POWERPC__))
+		/* pthread_setname_np is not there on <10.6 and all PPC.
+		So do nothing. */
+# else
 		pthread_setname_np((char*)name);
+# endif
 #elif defined(__FreeBSD__) || defined(__OpenBSD__)
 		pthread_set_name_np(pthread_self(), name);
 #elif defined(__NetBSD__)