assert macro not usable for PGI

In the current form, the assert macro is not usable, since it might
generate too long lines depending on the lenght of __FILE__ string.
This is a temporary fix to allow setting up tests on Minsky

test/Fortran/assert.h

@@ -40,7 +40,7 @@
 
 #define stringify_(x) "x"
 #define stringify(x) stringify_(x)
-#define assert(x) call x_a(x, stringify(x), __FILE__, __LINE__)
+#define assert(x) call x_a(x, stringify(x), "F", __LINE__)
 
 #define assert_elpa_ok(error_code) call x_ao(error_code, stringify(error_code), __FILE__, __LINE__)