Index: zorg/buildbot/builders/SanitizerBuilderWindows.py
===================================================================
--- zorg/buildbot/builders/SanitizerBuilderWindows.py
+++ zorg/buildbot/builders/SanitizerBuilderWindows.py
@@ -11,6 +11,7 @@
 from zorg.buildbot.builders.Util import getVisualStudioEnvironment
 from zorg.buildbot.builders.Util import extractSlaveEnvironment
 from zorg.buildbot.builders.Util import extractClangVersion
+from zorg.buildbot.commands.CmakeCommand import CmakeCommand
 from zorg.buildbot.commands.NinjaCommand import NinjaCommand
 
 def getSource(f,llvmTopDir='llvm'):
@@ -35,14 +36,13 @@
 
 def getSanitizerWindowsBuildFactory(
             clean=False,
-            cmake='cmake',
 
             # Default values for VS devenv and build configuration
             vs=r"""%VS120COMNTOOLS%""",
             config='Release',
             target_arch='x86',
 
-            extra_cmake_args=[]):
+            extra_configure_args= None):
 
     ############# PREPARING
     f = buildbot.process.factory.BuildFactory()
@@ -77,14 +77,29 @@
                 doStepIf=cleanBuildRequested
                 ))
 
-    f.addStep(ShellCommand(name='cmake',
-                           command=[cmake, "-G", "Ninja", "../llvm",
-                                    "-DCMAKE_BUILD_TYPE="+config,
-                                    "-DLLVM_ENABLE_ASSERTIONS=ON"]
-                                   + extra_cmake_args,
+    # Make a local copy of the configure args, as we are going to modify that.
+    if extra_configure_args:
+        cmake_args = extra_configure_args[:]
+    else:
+        cmake_args = list()
+
+    # Set proper defaults.
+    CmakeCommand.applyDefaultOptions(cmake_args, [
+        ('-G',                        'Ninja'),
+        ('-DCMAKE_BUILD_TYPE=',       config),
+        ('-DLLVM_ENABLE_ASSERTIONS=', 'ON')
+        ])
+
+    # Create configuration files with cmake
+    f.addStep(CmakeCommand(name="cmake-configure",
+                           options=cmake_args,
+                           path="../llvm",
                            haltOnFailure=True,
+                           description=["cmake configure"],
                            workdir=build_dir,
-                           env=Property('slave_env')))
+                           env=Property('slave_env'),
+                           doStepIf=FileDoesNotExist(
+                                        "./%s/CMakeCache.txt" % build_dir)))
 
     # Build compiler-rt first to speed up detection of Windows-specific
     # compiler-time errors in the sanitizer runtimes.
@@ -143,18 +158,32 @@
 
     # Get absolute path to clang-cl.
     clang_cl = "%(prop:workdir)s/" + build_dir + "/bin/clang-cl"
-    f.addStep(ShellCommand(name='cmake',
-                           command=[cmake, "-G", "Ninja", "../llvm",
-                                  "-DCMAKE_BUILD_TYPE="+config,
-                                  "-DLLVM_ENABLE_ASSERTIONS=ON",
-                                  Interpolate("-DCMAKE_C_COMPILER="+clang_cl),
-                                  Interpolate("-DCMAKE_CXX_COMPILER="+clang_cl),
-                                  "-DLLVM_USE_SANITIZER=Address",
-                                  "-DLLVM_USE_SANITIZE_COVERAGE=YES"]
-                                  + extra_cmake_args,
+
+    # Set proper defaults.
+    CmakeCommand.applyDefaultOptions(cmake_args, [
+        ('-G',                        'Ninja'),
+        ('-DCMAKE_BUILD_TYPE=',       config),
+        ('-DLLVM_ENABLE_ASSERTIONS=', 'ON'),
+        ])
+
+    # Some options are required for this build no matter what.
+    CmakeCommand.applyRequiredOptions(cmake_args, [
+        ('-DCMAKE_C_COMPILER=',           Interpolate(clang_cl)),
+        ('-DCMAKE_CXX_COMPILER=',         Interpolate(clang_cl)),
+        ('-DLLVM_USE_SANITIZER=',         'Address'),
+        ('-DLLVM_USE_SANITIZE_COVERAGE=', 'YES')
+        ])
+
+    # Create configuration files with cmake
+    f.addStep(CmakeCommand(name="cmake-fuzzer-configure",
+                           options=cmake_args,
+                           path="../llvm",
                            haltOnFailure=True,
+                           description=["cmake fuzzer configure"],
                            workdir=build_fuzzer_dir,
-                           env=Property('slave_env')))
+                           env=Property('slave_env'),
+                           doStepIf=FileDoesNotExist(
+                               "./%s/CMakeCache.txt" % build_fuzzer_dir)))
 
     # Build libFuzzer.
     f.addStep(NinjaCommand(name='build LLVMFuzzer',