[OE-core] Protection against ever-more-talented fools...

[Peter Seebach]

Time for some shell trivia!

Trivia point:  PATH=:/usr/bin and PATH=.:/usr/bin are equivalent.
Trivia point:  So are PATH=/bin::/usr/bin and PATH=/bin:.:/usr/bin
Trivia point:  People love to write stuff like:
  PATH=$(THAT_DIRECTORY):$PATH
Trivia point:  The shell expands undefined variables to empty strings.

Which is to say:

diff --git a/meta/classes/sanity.bbclass b/meta/classes/sanity.bbclass
index 687ddeb..1384592 100644
--- a/meta/classes/sanity.bbclass
+++ b/meta/classes/sanity.bbclass
@@ -298,8 +298,9 @@ def check_sanity(e):
         if not check_app_exists("qemu-arm", e.data):
             messages = messages + "qemu-native was in ASSUME_PROVIDED but the QEMU binaries (qemu-arm) can't be found in PATH"
 
-    if "." in data.getVar('PATH', e.data, True).split(":"):
-        messages = messages + "PATH contains '.' which will break the build, please remove this"
+    paths = data.getVar('PATH', e.data, True).split(":")
+    if "." in paths or "" in paths:
+        messages = messages + "PATH contains '.' or '', which will break the build, please remove this."
 
     if data.getVar('TARGET_ARCH', e.data, True) == "arm":
         # This path is no longer user-readable in modern (very recent) Linux

-- 
Listen, get this.  Nobody with a good compiler needs to be justified.