build: Stub out llvm-build utility tool.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143620 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/llvm-build/llvmbuild/main.py b/utils/llvm-build/llvmbuild/main.py
new file mode 100644
index 0000000..0d990a7
--- /dev/null
+++ b/utils/llvm-build/llvmbuild/main.py
@@ -0,0 +1,27 @@
+import os
+
+def main():
+    from optparse import OptionParser, OptionGroup
+    parser = OptionParser("usage: %prog [options]")
+    parser.add_option("", "--source-root", dest="source_root", metavar="PATH",
+                      help="Path to the LLVM source (inferred if not given)",
+                      action="store", default=None)
+    (opts, args) = parser.parse_args()
+
+    # Determine the LLVM source path, if not given.
+    source_root = opts.source_root
+    if source_root:
+        if not os.path.exists(os.path.join(source_root, 'lib', 'VMCore',
+                                           'Function.cpp')):
+            parser.error('invalid LLVM source root: %r' % source_root)
+    else:
+        llvmbuild_path = os.path.dirname(__file__)
+        llvm_build_path = os.path.dirname(llvmbuild_path)
+        utils_path = os.path.dirname(llvm_build_path)
+        source_root = os.path.dirname(utils_path)
+        if not os.path.exists(os.path.join(source_root, 'lib', 'VMCore',
+                                           'Function.cpp')):
+            parser.error('unable to infer LLVM source root, please specify')
+
+if __name__=='__main__':
+    main()