Bug 1444141 - part 3 - fix exports of PATH in sm-tooltool-config.sh; r=sfink

TOOLTOOL_CHECKOUT is typically `.`, which doesn't work so great for
adding things to $PATH.  We need to turn everything we're adding to
$PATH into absolute paths, so $PATH actually works properly.

taskcluster/scripts/builder/sm-tooltool-config.sh

@@ -63,5 +63,9 @@ BROWSER_PLATFORM=$PLATFORM_OS$BITS
 
 # Add all the tooltool binaries to our $PATH.
 for bin in $TOOLTOOL_CHECKOUT/*/bin $TOOLTOOL_CHECKOUT/VC/bin/Hostx64/x86; do
-    export PATH="$bin:$PATH"
+    if [ ! -d "$bin" ]; then
+        continue
+    fi
+    absbin=$(cd "$bin" && pwd)
+    export PATH="$absbin:$PATH"
 done