Fix checking if we are compiling for Linux.

Author: Seppo Takalo

Makefile

@@ -1,8 +1,15 @@
-ifeq ($(shell uname -s),Linux)
+
+# Check if we are compiling for Linux using GCC
+ifneq (,$(findstring gcc,$(CC)))
+TARGET_IS_LINUX := $(shell $(CC) -dM -E - < /dev/null | grep __linux >/dev/null && echo "yes" || echo "no")
+endif
+
+ifeq (yes,$(TARGET_IS_LINUX))
 SRCS := $(wildcard linux/*)
 else
 SRCS := $(wildcard source/*)
 endif
+
 LIB := librand.a
 EXPORT_HEADERS := mbed-client-randlib