testsdk: Avoid PATH contamination

The autobuilder has been seeing increasing numbers of testsdk failures
where xz was 'missing':

ERROR: core-image-sato-1.0-r0 do_testsdk: Couldn't install the SDK:
Error: xz is required for installation of this SDK, please install it first

This is probably due to xz and it's libraries not being in the sysroots
in a way which works without races.

Since the SDK should be using the host, fix this. The eSDK already does
this to solve a similar problem so copy the code from there.

(From OE-Core rev: 39ac3439dfdf2afa67abed4bd32aeb3c14979ded)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/sdk/testsdk.py

@@ -79,6 +79,9 @@ class TestSDK(TestSDKBase):
         # sdk use network for download projects for build
         export_proxies(d)
 
+        # We need the original PATH for testing the eSDK, not with our manipulations
+        os.environ['PATH'] = d.getVar("BB_ORIGENV", False).getVar("PATH")
+
         tcname = self.get_tcname(d)
 
         if not os.path.exists(tcname):