SetupForDevelopment: Fix run through Windows file association
The Git for Windows installer offers to create a file association
for .sh
files that will run them with the MSYS bash that comes
with the distribution. Running SetupForDevelopment.sh
this way
causes backslashes (\
) to appear in the BASH_SOURCE
variable
and breaks our idiom to find the directory containing the script.
Update the code to replace backslashes with forward slashes.