added __SHADY__ macro

Author: Hugobros3

src/driver/vcc.c

@@ -81,7 +81,7 @@ int main(int argc, char** argv) {
     growy_append_string(g, "clang");
     char* self_path = get_executable_location();
     char* working_dir = strip_path(self_path);
-    growy_append_formatted(g, " -c -emit-llvm -S -g -O0 -ffreestanding -Wno-main-return-type -Xclang -fpreserve-vec3-type --target=spir64-unknown-unknown -isystem\"%s/../share/vcc/include/\"", working_dir);
+    growy_append_formatted(g, " -c -emit-llvm -S -g -O0 -ffreestanding -Wno-main-return-type -Xclang -fpreserve-vec3-type --target=spir64-unknown-unknown -isystem\"%s/../share/vcc/include/\" -D__SHADY__=1", working_dir);
     free(working_dir);
     free(self_path);
     growy_append_formatted(g, " -o %s", vcc_options.tmp_filename);

vcc-std/include/shady.h

@@ -1,6 +1,10 @@
 #ifndef _SHADY_H
 #define _SHADY_H
 
+#ifndef __SHADY__
+#error "This header can only be used with Vcc"
+#endif
+
 #define vertex_shader __attribute__((annotate("shady::entry_point::Vertex")))
 #define fragment_shader __attribute__((annotate("shady::entry_point::Fragment")))
 #define compute_shader  __attribute__((annotate("shady::entry_point::Compute")))