Update build.libgit2sharp.sh

Updated the message about why the LD_LIBRARY_PATH setting is needed, and made
it clearer that the current working directory is the value that is required.

Author: bording

build.libgit2sharp.sh

@@ -2,10 +2,11 @@
 
 EXTRADEFINE="$1"
 
-# Exporting a dummy value with ':' works around a linux mono bug where it
-# can't find libgit when the libgit2sharp assembly has been shadow copied.
-# This appears to only be a problem on linux and not osx.
-export LD_LIBRARY_PATH=:
+# Setting LD_LIBRARY_PATH to the current working directory is needed to run
+# the tests successfully in linux. Without this, mono can't find libgit when
+# the libgit2sharp assembly has been shadow copied. OS X includes the current
+# working directory in its library search path, so it works without this value.
+export LD_LIBRARY_PATH=.
 
 # Required for NuGet package restore to run.
 mozroots --import --sync