Index: zorg/buildbot/builders/SanitizerBuilderWindows.py
===================================================================
--- zorg/buildbot/builders/SanitizerBuilderWindows.py
+++ zorg/buildbot/builders/SanitizerBuilderWindows.py
@@ -141,8 +141,11 @@
                           extract_fn=extractSlaveEnvironment,
                           env=Property('slave_env')))
 
-    # Get absolute path to clang-cl.
-    clang_cl = "%(workdir)s/" + build_dir + "/bin/clang-cl"
+    # Use relative path to clang-cl.  We would just be basing it off of
+    # %(workdir) anyway, but %(workdir) will confuse the setting of
+    # CMAKE_CXX_COMPILER and CMAKE_C_COMPILER.  Since we're already inside of
+    # %(workdir) (by definition), a relative path should be fine.
+    clang_cl = "../" + build_dir + "/bin/clang-cl"
     f.addStep(ShellCommand(name='cmake',
                            command=[cmake, "-G", "Ninja", "../llvm",
                                "-DCMAKE_BUILD_TYPE="+config,