[LLDB] Make API tests to run using MSYS tools

MSYS 'uname' on windows returns "MSYS_NT*" instead of windows32 and also
MSYS 'pwd' returns non-windows path string.
This patch fixes Makefile.rules to make adjustments required to run LLDB
API tests using MSYS tools.

Differential Revision: https://reviews.llvm.org/D133002

lldb/packages/Python/lldbsuite/test/make/Makefile.rules

@@ -49,15 +49,21 @@ LLDB_BASE_DIR := $(THIS_FILE_DIR)/../../../../../
 #----------------------------------------------------------------------
 # If OS is not defined, use 'uname -s' to determine the OS name.
 #
-# uname on Windows gives "windows32" or "server version windows32", but most
-# environments standardize on "Windows_NT", so we'll make it consistent here.
+# GNUWin32 uname gives "windows32" or "server version windows32" while
+# some versions of MSYS uname return "MSYS_NT*", but most environments
+# standardize on "Windows_NT", so we'll make it consistent here. 
 # When running tests from Visual Studio, the environment variable isn't
 # inherited all the way down to the process spawned for make.
 #----------------------------------------------------------------------
 HOST_OS := $(shell uname -s)
 ifneq (,$(findstring windows32,$(HOST_OS)))
 	HOST_OS := Windows_NT
 endif
+
+ifneq (,$(findstring MSYS_NT,$(HOST_OS)))
+	HOST_OS := Windows_NT
+endif
+
 ifeq "$(OS)" ""
 	OS := $(HOST_OS)
 endif
@@ -68,9 +74,12 @@ endif
 # Some versions of make on Windows will search for other shells such as
 # C:\cygwin\bin\sh.exe. This shell fails for numerous different reasons
 # so default to using cmd.exe.
+# Also reset BUILDDIR value because "pwd" returns cygwin or msys path
+# which needs to be converted to windows path.
 #----------------------------------------------------------------------
 ifeq "$(OS)" "Windows_NT"
 	SHELL = $(WINDIR)\system32\cmd.exe
+	BUILDDIR := $(shell echo %cd%)
 endif
 
 #----------------------------------------------------------------------