Compute Python library suffix in CMakeLists.txt

Introduce LLDB_PY_LIB_SUFFIX and use it in various places in the
build.  This lets the x.py-based build work properly without having to
set LLVM_LIBDIR_SUFFIX.

See https://bugs.llvm.org/show_bug.cgi?id=18957 for some discussion.

Author: tromey

lldb/CMakeLists.txt

@@ -30,6 +30,14 @@ if (WIN32)
   add_definitions(-D_ENABLE_EXTENDED_ALIGNED_STORAGE)
 endif()
 
+if (NOT LLDB_DISABLE_PYTHON)
+   execute_process(
+     COMMAND
+        ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/scripts/get_libdir_suffix.py
+     OUTPUT_VARIABLE LLDB_PY_LIB_SUFFIX)
+endif ()
+
+add_subdirectory(docs)
 if (NOT LLDB_DISABLE_PYTHON)
   add_subdirectory(scripts)
 endif ()
@@ -186,7 +194,7 @@ if (NOT LLDB_DISABLE_PYTHON)
                --cfgBldDir=${lldb_scripts_dir}
                --prefix=${CMAKE_BINARY_DIR}
                --cmakeBuildConfiguration=${CMAKE_CFG_INTDIR}
-               --lldbLibDir=lib${LLVM_LIBDIR_SUFFIX}
+               --lldbLibDir=lib${LLDB_PY_LIB_SUFFIX}
                ${use_python_wrapper_from_src_dir}
                ${use_six_py_from_system}
         VERBATIM

lldb/scripts/CMakeLists.txt

@@ -44,7 +44,7 @@ if(NOT LLDB_BUILD_FRAMEWORK)
   endif()
 
   set(SWIG_PYTHON_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${swig_python_subdir})
-  set(SWIG_INSTALL_DIR lib${LLVM_LIBDIR_SUFFIX})
+  set(SWIG_INSTALL_DIR lib${LLDB_PY_LIB_SUFFIX})
 
   # Install the LLDB python module
   install(DIRECTORY ${SWIG_PYTHON_DIR} DESTINATION ${SWIG_INSTALL_DIR})

lldb/scripts/get_libdir_suffix.py

@@ -0,0 +1,33 @@
+import distutils.sysconfig
+import os
+import platform
+import re
+import sys
+
+
+def get_python_libdir_suffix():
+    """Returns the appropropriate python libdir suffix.
+
+    @return the python libdir suffix, normally either "" or "64".
+    """
+    if platform.system() != 'Linux':
+        return ""
+
+    # We currently have a bug in lldb -P that does not account for
+    # architecture variants in python paths for
+    # architecture-specific modules.  Handle the lookup here.
+    # When that bug is fixed, we should just ask lldb for the
+    # right answer always.
+    arch_specific_libdir = distutils.sysconfig.get_python_lib(True, False)
+    split_libdir = arch_specific_libdir.split(os.sep)
+    lib_re = re.compile(r"^lib.+$")
+
+    for i in range(len(split_libdir)):
+        match = lib_re.match(split_libdir[i])
+        if match is not None:
+            return split_libdir[i][3:]
+    return ""
+
+if __name__ == '__main__':
+    sys.stdout.write(get_python_libdir_suffix())
+    sys.exit(0)