modify Xcode build to use cmake/ninja for internal llvm/clang

This change restores the Xcode build to working after Makefile support
was stripped from LLVM and clang recently.

With this change, the Xcode build now requires cmake (2.8.12.2+).
The cmake must either be on the path that Xcode sees, or it must
exist in one of the following locations:

* /usr/local/bin/cmake
* /opt/local/bin/cmake
* $HOME/bin/cmake

If the ninja build tool is present on the path, it will be used.
If not, ninja will be cloned (via git), bootstrap-built, and
used for the llvm/clang build.

LLDB now requires a minimum deployment target of OS X 10.9.  Prior
to this, it was 10.8.  The llvm/clang cmake build will not run
with Xcode 7.2 or Xcode 7.3 beta's compiler with the minimum
deployment target set to anything lower than 10.9.  This is
related to #include <atomic>.

When llvm or clang source code does not exist in the lldb tree,
it will be cloned via git using http://llvm.org/git/{project}.git.
Previously it used SVN.  If this causes any heartache, we can
make this smarter, autodetect an embedded svn and use svn instead.
(And/or use SVN if a git command is not available).

This change also fixes an lldb-mi linkage failure (needed
libncurses) as exposed by one of the LLVM libs.

llvm-svn: 259027
diff --git a/lldb/scripts/Xcode/lldbbuild.py b/lldb/scripts/Xcode/lldbbuild.py
new file mode 100644
index 0000000..cf79a3e
--- /dev/null
+++ b/lldb/scripts/Xcode/lldbbuild.py
@@ -0,0 +1,135 @@
+import os
+import subprocess
+
+#### UTILITIES ####
+
+def enum (*sequential, **named):
+    enums = dict(zip(sequential, range(len(sequential))), **named)
+    return type('Enum', (), enums)
+
+#### SETTINGS ####
+
+#### INTERFACE TO THE XCODEPROJ ####
+
+def lldb_source_path ():
+    return os.environ.get('SRCROOT')
+
+def expected_llvm_build_path ():
+    if build_type() == BuildType.Xcode:
+        return package_build_path()
+    else:
+        return os.path.join(os.environ.get('LLDB_PATH_TO_LLVM_BUILD'), package_build_dir_name("llvm"))
+
+def archives_txt ():
+    return os.path.join(expected_package_build_path(), "archives.txt")
+
+def expected_package_build_path ():
+    return os.path.abspath(os.path.join(expected_llvm_build_path(), ".."))
+
+def architecture ():
+    platform_name = os.environ.get('RC_PLATFORM_NAME')
+    if not platform_name:
+        platform_name = os.environ.get('PLATFORM_NAME')
+    platform_arch = os.environ.get('ARCHS').split()[-1]
+    return platform_name + "-" + platform_arch
+
+def lldb_configuration ():
+    return os.environ.get('CONFIGURATION')
+
+def llvm_configuration ():
+    return os.environ.get('LLVM_CONFIGURATION')
+
+def llvm_build_dirtree ():
+    return os.environ.get('LLVM_BUILD_DIRTREE')
+
+# Edit the code below when adding build styles.
+
+BuildType = enum('Xcode')                # (Debug,DebugClang,Release)
+
+def build_type ():
+    return BuildType.Xcode
+
+#### VCS UTILITIES ####
+
+VCS = enum('git',
+           'svn')
+
+def run_in_directory(args, path):
+    return subprocess.check_output(args, cwd=path)
+
+class Git:
+    def __init__ (self, spec):
+        self.spec = spec
+    def status (self):
+        return run_in_directory(["git", "branch", "-v"], self.spec['root'])
+    def diff (self):
+        return run_in_directory(["git", "diff"], self.spec['root'])
+    def check_out (self):
+        run_in_directory(["git", "clone", self.spec['url'], self.spec['root']], lldb_source_path())
+        run_in_directory(["git", "fetch", "--all"], self.spec['root'])
+        run_in_directory(["git", "checkout", self.spec['ref']], self.spec['root'])
+
+class SVN:
+    def __init__ (self, spec):
+        self.spec = spec
+    def status (self):
+        return run_in_directory(["svn", "info"], self.spec['root'])
+    def diff (self):
+        return run_in_directory(["svn", "diff"], self.spec['root'])
+    # TODO implement check_out
+
+def vcs (spec):
+    if spec['vcs'] == VCS.git:
+        return Git(spec)
+    elif spec['vcs'] == VCS.svn:
+        return SVN(spec)
+    else:
+        return None
+
+#### SOURCE PATHS ####
+
+def llvm_source_path ():
+    if build_type() == BuildType.Xcode:
+        return os.path.join(lldb_source_path(), "llvm")
+
+def clang_source_path ():
+    if build_type() == BuildType.Xcode:
+        return os.path.join(llvm_source_path(), "tools", "clang")
+
+def ninja_source_path ():
+    if build_type() == BuildType.Xcode:
+        return os.path.join(lldb_source_path(), "ninja")
+
+#### BUILD PATHS ####
+
+def packages ():
+    return ["llvm"]
+
+def package_build_dir_name (package):
+    return package + "-" + architecture()
+
+def expected_package_build_path_for (package):
+    if build_type() == BuildType.Xcode:
+        if package != "llvm":
+            raise("On Xcode build, we only support the llvm package: requested {}".format(package))
+        return package_build_path()
+    return os.path.join(expected_package_build_path(), package_build_dir_name(package))
+
+def expected_package_build_paths ():
+    return [expected_package_build_path_for(package) for package in packages()]
+
+def library_path (build_path):
+    return build_path + "/lib"
+
+def library_paths ():
+    if build_type() == BuildType.Xcode:
+        package_build_paths = [package_build_path()]
+    else:
+        package_build_paths = expected_package_build_paths()
+    return [library_path(build_path) for build_path in package_build_paths]
+
+def package_build_path ():
+    return os.path.join(
+        llvm_build_dirtree(),
+        os.environ["LLVM_CONFIGURATION"],
+        os.environ["CURRENT_ARCH"])