[lldb][CMake] If make isn't found, print a warning but don't error out (llvm#111531)

Bot maintainers should be aware and it became too much of a burden
for developers. In particular on Windows, where make.exe won't be
found in Path typically.

Author: weliveindetail

lldb/test/API/CMakeLists.txt

@@ -73,9 +73,9 @@ else()
     message(STATUS "Found make: ${LLDB_DEFAULT_TEST_MAKE}")
   else()
     message(STATUS "Not found: make")
-    message(SEND_ERROR
-          "LLDB tests require 'make' tool. Please pass via `LLDB_TEST_MAKE` "
-          "(or otherwise disable tests with `LLDB_INCLUDE_TESTS=OFF`)")
+    message(WARNING
+          "Many LLDB API tests require 'make' tool. Please provide it in Path "
+          "or pass via LLDB_TEST_MAKE.")
   endif()
 endif()