unix: add -v to compiler and linker flags

I'm trying to debug why Python 3.8 builds are using the 11.0 SDK.
I think it has something to do with the default sysroot and search
paths baked into Clang. Let's build in verbose mode so the search
paths are printed and we can confirm our hypothesis.

Author: indygreg

cpython-unix/build.py

@@ -169,6 +169,9 @@ def add_target_env(env, build_platform, target_triple, build_env):
         extra_host_cflags.extend(["-isysroot", host_sdk_path])
         extra_host_ldflags.extend(["-isysroot", host_sdk_path])
 
+    extra_target_cflags.append("-v")
+    extra_target_ldflags.append("-v")
+
     env["EXTRA_HOST_CFLAGS"] = " ".join(extra_host_cflags)
     env["EXTRA_HOST_LDFLAGS"] = " ".join(extra_host_ldflags)
     env["EXTRA_TARGET_CFLAGS"] = " ".join(extra_target_cflags)