Add AIX support to Path.inc, Host.h, and CMake build files.

[chandlerc]

LGTM, some of these were in a much older patch that i found and LGTM'ed as well.

[apaprocki]

I don't have access to land this, can someone else do it?

CMakeLists.txt

 # check its symbols. This is wasteful (the check was done when foo.so
 # was created) and can fail since it is not the dynamic linker and
 # doesn't know how to handle search paths correctly.
-if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS|AIX")
   set(CMAKE_EXE_LINKER_FLAGS
       "${CMAKE_EXE_LINKER_FLAGS} -Wl,-allow-shlib-undefined")
 endif()

cmake/modules/AddLLVM.cmake

       COMMENT "Creating export file for ${target_name}")
     set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                  LINK_FLAGS " -Wl,-exported_symbols_list,${CMAKE_CURRENT_BINARY_DIR}/${native_export_file}")
+  elseif(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+    set_property(TARGET ${target_name} APPEND_STRING PROPERTY
+                 LINK_FLAGS " -Wl,-bE:${export_file}")
   elseif(LLVM_HAVE_LINK_VERSION_SCRIPT)
     # Gold and BFD ld require a version script rather than a plain list.
     set(native_export_file "${target_name}.exports")

 
     # Pass -O3 to the linker. This enabled different optimizations on different
     # linkers.
-    if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin|SunOS" OR WIN32))
+    if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin|SunOS|AIX" OR WIN32))
       set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-O3")
     endif()

cmake/modules/HandleLLVMOptions.cmake

   if(UNIX)
     set(LLVM_ON_WIN32 0)
     set(LLVM_ON_UNIX 1)
-    if(APPLE)
+    if(APPLE OR ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
       set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
-    else(APPLE)
+    else()
       set(LLVM_HAVE_LINK_VERSION_SCRIPT 1)
-    endif(APPLE)
+    endif()
   else(UNIX)
     MESSAGE(SEND_ERROR "Unable to determine platform")
   endif(UNIX)

include/llvm/Support/Host.h

 
 #if defined(__linux__) || defined(__GNU__) || defined(__HAIKU__)
 #include <endian.h>
+#elif defined(_AIX)
+#include <sys/machine.h>
 #else
 #if !defined(BYTE_ORDER) && !defined(LLVM_ON_WIN32)
 #include <machine/endian.h>

lib/Support/Unix/Path.inc

 namespace fs {
 #if defined(__FreeBSD__) || defined (__NetBSD__) || defined(__Bitrig__) || \
     defined(__OpenBSD__) || defined(__minix) || defined(__FreeBSD_kernel__) || \
-    defined(__linux__) || defined(__CYGWIN__) || defined(__DragonFly__)
+    defined(__linux__) || defined(__CYGWIN__) || defined(__DragonFly__) || \
+    defined(_AIX)
 static int
 test_dir(char ret[PATH_MAX], const char *dir, const char *bin)
 {  

   }
 #elif defined(__FreeBSD__) || defined (__NetBSD__) || defined(__Bitrig__) || \
       defined(__OpenBSD__) || defined(__minix) || defined(__DragonFly__) || \
-      defined(__FreeBSD_kernel__)
+      defined(__FreeBSD_kernel__) || defined(_AIX)
   char exe_path[PATH_MAX];
 
   if (getprogpath(exe_path, argv0) != NULL)