Allow relative CxxBuiltinDirectories not just under crosstool or sysroot.

cxx_builtin_include directories which start with "%workspace%/" are taken
to be relative to the build workspace, and not relative to crosstool-top.

RELNOTES[NEW]: cpxx_builtin_include_directory specifications allow more flexibility.

--
MOS_MIGRATED_REVID=105789270

1 files changed, 3 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
index 765387fc18..80f1644ece 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
@@ -849,6 +849,7 @@ public class CppConfiguration extends BuildConfiguration.Fragment {
   }
 
   private static final PathFragment SYSROOT_FRAGMENT = new PathFragment("%sysroot%");
+  private static final PathFragment WORKSPACE_FRAGMENT = new PathFragment("%workspace%");
 
   /**
    * Resolve the given include directory. If it is not absolute, it is
@@ -867,6 +868,8 @@ public class CppConfiguration extends BuildConfiguration.Fragment {
             + "default_sysroot option is set");
       }
       return sysroot.getRelative(path.relativeTo(SYSROOT_FRAGMENT));
+    } else if (path.startsWith(WORKSPACE_FRAGMENT)) {
+      return path.subFragment(1, path.segmentCount());
     } else {
       return crosstoolTopPathFragment.getRelative(path);
     }