Fix for #1271, set_file_prefix_map attribute (#1288)

Author: aaron-michaux

foreign_cc/private/cc_toolchain_util.bzl

@@ -306,6 +306,11 @@ def get_flags_info(ctx, link_output_file = None):
             ),
         ),
     )
+
+    if "set_file_prefix_map" in dir(ctx.attr) and ctx.attr.set_file_prefix_map:
+        copts.append("-ffile-prefix-map=$EXT_BUILD_ROOT=.")
+        cxxopts.append("-ffile-prefix-map=$EXT_BUILD_ROOT=.")
+
     return CxxFlagsInfo(
         cc = _convert_flags(cc_toolchain_.compiler, _add_if_needed(flags.cc, copts)),
         cxx = _convert_flags(cc_toolchain_.compiler, _add_if_needed(flags.cxx, cxxopts)),

foreign_cc/private/framework.bzl

@@ -201,6 +201,14 @@ CC_EXTERNAL_RULE_ATTRIBUTES = {
         doc = "Optional part of the shell script to be added after the make commands",
         mandatory = False,
     ),
+    "set_file_prefix_map": attr.bool(
+        doc = (
+            "Use -ffile-prefix-map with the intention to remove the sandbox path from " +
+            "debug symbols"
+        ),
+        mandatory = False,
+        default = False,
+    ),
     "targets": attr.string_list(
         doc = (
             "A list of targets with in the foreign build system to produce. An empty string (`\"\"`) will result in " +