Check for rt and pthread libraries before linking

This fixes building on Android which does not have separate librt
or libpthread libraries.

Signed-off-by: Fredrik Fornwall <fredrik@fornwall.net>

lib/CMakeLists.txt

@@ -7,7 +7,12 @@ if (${WITH_THREADING} STREQUAL ON)
 		set (PTHREAD_LIBRARIES C:\\pthreads\\Pre-built.2\\lib\\x86\\pthreadVC2.lib)
 		set (PTHREAD_INCLUDE_DIR C:\\pthreads\\Pre-built.2\\include)
 	else (WIN32)
-		set (PTHREAD_LIBRARIES pthread)
+		find_library(LIBPTHREAD pthread)
+		if (LIBPTHREAD)
+			set (PTHREAD_LIBRARIES pthread)
+		else (LIBPTHREAD)
+			set (PTHREAD_LIBRARIES "")
+		endif()
 		set (PTHREAD_INCLUDE_DIR "")
 	endif (WIN32)
 else (${WITH_THREADING} STREQUAL ON)
@@ -44,7 +49,10 @@ add_library(libmosquitto SHARED
 set (LIBRARIES ${OPENSSL_LIBRARIES} ${PTHREAD_LIBRARIES})
 
 if (UNIX AND NOT APPLE)
-	set (LIBRARIES ${LIBRARIES} rt)
+	find_library(LIBRT rt)
+	if (LIBRT)
+		set (LIBRARIES ${LIBRARIES} rt)
+	endif (LIBRT)
 endif (UNIX AND NOT APPLE)
 
 if (WIN32)

src/CMakeLists.txt

@@ -86,7 +86,11 @@ if (UNIX)
 	if (APPLE)
 		set (MOSQ_LIBS ${MOSQ_LIBS} dl m)
 	else (APPLE)
-		set (MOSQ_LIBS ${MOSQ_LIBS} rt dl m)
+		set (MOSQ_LIBS ${MOSQ_LIBS} dl m)
+		find_library(LIBRT rt)
+		if (LIBRT)
+			set (MOSQ_LIBS ${MOSQ_LIBS} rt)
+		endif (LIBRT)
 	endif (APPLE)
 endif (UNIX)