Fails to run when executed using `sh`

Several projects don't allow executable files in their version control system due to platform compatibility concerns. For instance, OpenJDK doesn't allow executables to be committed in Git repositories[1]. Hence, Maven Wrapper should be runnable as an argument to `sh`, though it is not:

sh mvnw
mvnw: 109: cannot open mvnw/.mvn/wrapper/maven-wrapper.properties: No such file

due to the following line:

"${0%/*}/.mvn/wrapper/maven-wrapper.properties"

I expect there to be more issues due to `$0` usage assuming the script is executed as an executable – did not check.
 
[1] See the `Executable files are not allowed (file: mvnw)` error generated by the Skara bot of OpenJDK in this PR attempting to integrate Maven Wrapper to JMH: https://github.com/openjdk/jmh/pull/154