[lldb][test] Set target and host OS for API tests in case of remote testing

Makefile.rules uses HOST_OS and OS variables for determining host and target
OSes for API tests compilation.

This commit moves the platform detection logic from Makefile to Python lldb
test suite.

    This is useful for the case of Windows-to-Linux cross-testing.

Author: dzhidzhoev

lldb/packages/Python/lldbsuite/test/lldbplatformutil.py

@@ -92,11 +92,28 @@ def match_android_device(device_arch, valid_archs=None, valid_api_levels=None):
 
 
 def finalize_build_dictionary(dictionary):
+    # Provide uname-like platform name
+    platform_name_to_uname = {
+        "linux": "Linux",
+        "netbsd": "NetBSD",
+        "freebsd": "FreeBSD",
+        "windows": "Windows_NT",
+        "macosx": "Darwin",
+        "darwin": "Darwin",
+    }
+
+    if dictionary is None:
+        dictionary = {}
     if target_is_android():
-        if dictionary is None:
-            dictionary = {}
         dictionary["OS"] = "Android"
         dictionary["PIE"] = 1
+    elif platformIsDarwin():
+        dictionary["OS"] = "Darwin"
+    else:
+        dictionary["OS"] = platform_name_to_uname[getPlatform()]
+
+    dictionary["HOST_OS"] = platform_name_to_uname[getHostPlatform()]
+
     return dictionary
 
 

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

@@ -55,7 +55,10 @@ LLDB_BASE_DIR := $(THIS_FILE_DIR)/../../../../../
 # When running tests from Visual Studio, the environment variable isn't
 # inherited all the way down to the process spawned for make.
 #----------------------------------------------------------------------
-HOST_OS := $(shell uname -s)
+ifeq "$(HOST_OS)" ""
+  HOST_OS := $(shell uname -s)
+endif
+
 ifneq (,$(findstring windows32,$(HOST_OS)))
 	HOST_OS := Windows_NT
 endif