Propagate cc_library defines to clang (#3271)

Currently if `cc_library` uses `defines = [...]`, it won't be picked by
bindgen.

This is a 2-line fix to add the support (with tests).

Co-authored-by: UebelAndre <github@uebelandre.com>

Author: nbdd0121

extensions/bindgen/private/bindgen.bzl

@@ -307,6 +307,10 @@ def _rust_bindgen_impl(ctx):
             open_arg = True
             continue
 
+    # Propagated defines should be made visible to clang
+    for define in ctx.attr.cc_lib[CcInfo].compilation_context.defines.to_list():
+        args.add("-D" + define)
+
     _, _, linker_env = get_linker_and_args(ctx, "bin", cc_toolchain, feature_configuration, None)
     env.update(**linker_env)
 

extensions/bindgen/test/integration/simple/BUILD.bazel

@@ -11,5 +11,6 @@ cc_library(
     name = "simple",
     srcs = ["simple.cc"],
     hdrs = ["simple.h"],
+    defines = ["SIMPLE_DEFINE=1"],
     visibility = ["//test/integration:__pkg__"],
 )

extensions/bindgen/test/integration/simple/simple.h

@@ -9,8 +9,12 @@
 
 #include <stdint.h>
 
+#ifdef SIMPLE_DEFINE
+
 static const int64_t SIMPLE_VALUE = 42;
 
+#endif
+
 EXTERN_C const int64_t simple_function();
 
 static inline int64_t simple_static_function() { return 84; }