build: Added DefinePlatformDefaults cmake file.

cmake/Modules/DefinePlatformDefaults.cmake

@@ -0,0 +1,21 @@
+# Set system vars
+
+if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+    set(LINUX TRUE)
+endif(CMAKE_SYSTEM_NAME MATCHES "Linux")
+
+if (CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
+    set(FREEBSD TRUE)
+endif (CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
+
+if (CMAKE_SYSTEM_NAME MATCHES "OpenBSD")
+    set(OPENBSD TRUE)
+endif (CMAKE_SYSTEM_NAME MATCHES "OpenBSD")
+
+if (CMAKE_SYSTEM_NAME MATCHES "NetBSD")
+    set(NETBSD TRUE)
+endif (CMAKE_SYSTEM_NAME MATCHES "NetBSD")
+
+if (CMAKE_SYSTEM_NAME MATCHES "(Solaris|SunOS)")
+    set(SOLARIS TRUE)
+endif (CMAKE_SYSTEM_NAME MATCHES "(Solaris|SunOS)")