Fix vswhere.exe discovery for non-default Visual Studio installations

Closes #1235

Signed-off-by: Aditya kumar singh <143548997+Adityakk9031@users.noreply.github.com>

Author: Adityakk9031

warp/_src/build_dll.py

@@ -200,6 +200,10 @@ def find_host_compiler() -> str:
                 print("Warning: VCToolsVersion not set after running vcvars64.bat")
             return ""
         cl_version = vc_tools_version.split(".")
+        if len(cl_version) < 2:
+            if verbose_cmd:
+                print(f"Warning: Invalid VCToolsVersion format: {vc_tools_version}")
+            return ""
 
         # ensure at least VS2019 version, see list of MSVC versions here https://en.wikipedia.org/wiki/Microsoft_Visual_C%2B%2B
         cl_required_major = 14