Merge pull request #1600 from adamgreen/fixIssue1599

Fix issue #1599

Author: 0xc0170

libraries/mbed/common/retarget.cpp

@@ -121,8 +121,10 @@ static inline int openmode_to_posix(int openmode) {
     if (openmode & _LLIO_CREAT ) posix |= O_CREAT;
     if (openmode & _LLIO_APPEND) posix |= O_APPEND;
     if (openmode & _LLIO_TRUNC ) posix |= O_TRUNC;
+#elif defined(TOOLCHAIN_GCC)
+    posix &= ~O_BINARY;
 #endif
-    return posix & ~O_BINARY;
+    return posix;
 }
 
 extern "C" FILEHANDLE PREFIX(_open)(const char* name, int openmode) {