--- a/tools/cpp/unix_cc_configure.bzl
+++ b/tools/cpp/unix_cc_configure.bzl
@@ -147,9 +147,18 @@ def get_escaped_cxx_inc_directories(repository_ctx, cc, additional_flags = []):
   else:
     inc_dirs = result.stderr[index1 + 1:index2].strip()
 
-  return [_prepare_include_path(repository_ctx, _cxx_inc_convert(p))
-          for p in inc_dirs.split("\n")]
+  default_inc_directories = [
+    _prepare_include_path(repository_ctx, _cxx_inc_convert(p))
+      for p in inc_dirs.split("\n")
+  ]
+ 
+  env = repository_ctx.os.environ
+  if "SPACK_INCLUDE_DIRS" in env:
+    for path in env["SPACK_INCLUDE_DIRS"].split(":"):
+      default_inc_directories.append(path)
+
+  return default_inc_directories
 

 def _is_option_supported(repository_ctx, cc, option):