Heuristically path map copts and defines

src/main/java/com/google/devtools/build/lib/actions/PathMapper.java

@@ -127,6 +127,13 @@ default ExceptionlessMapFn<Object> getMapFn(@Nullable String previousFlag) {
     return MapFn.DEFAULT;
   }
 
+  /**
+   * Heuristically maps all path-like strings in the given argument.
+   */
+  default String mapHeuristically(String arg) {
+    return arg;
+  }
+
   /**
    * Returns a {@link FileRootApi} representing the new root of the given artifact after mapping.
    *

src/main/java/com/google/devtools/build/lib/analysis/actions/StrippingPathMapper.java

@@ -189,6 +189,11 @@ public ExceptionlessMapFn<Object> getMapFn(@Nullable String previousFlag) {
     return MapFn.DEFAULT;
   }
 
+  @Override
+  public String mapHeuristically(String arg) {
+    return argStripper.strip(arg);
+  }
+
   @Override
   public FileRootApi mapRoot(Artifact artifact) {
     if (Objects.equals(artifact.getRoot(), outputArtifactRoot)) {

src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainVariables.java

@@ -1043,7 +1043,7 @@ public ImmutableList<VariableValue> getSequenceValue(
       ImmutableList.Builder<VariableValue> sequences =
           ImmutableList.builderWithExpectedSize(values.size());
       for (String value : values) {
-        sequences.add(new StringValue(value));
+        sequences.add(new StringValue(pathMapper.mapHeuristically(value)));
       }
       return sequences.build();
     }

src/test/shell/bazel/path_mapping_test.sh

@@ -530,6 +530,7 @@ cc_library(
     name = "utils",
     srcs = ["dir/utils.cc"],
     hdrs = ["dir/utils.h"],
+    defines = ["MY_FILE=\\\"+$(execpath dir/utils.cc)+\\\""],
     include_prefix = "other_dir",
     strip_include_prefix = "dir",
     visibility = ["//visibility:public"],
@@ -615,7 +616,13 @@ EOF
   cat > "$pkg/common/utils/utils.cc.tpl" <<'EOF'
 #include "utils.h"
 
+#include <cstdlib>
+#include <iostream>
+
 std::string AsGreeting(const std::string& name) {
+  if (std::string(MY_FILE).find("-out/cfg/") == std::string::npos) {
+    std::cerr << "Expected path to contain '-out/cfg/'" << std::endl;
+  }
   return "{GREETING}, " + name + "!";
 }
 EOF