When creating your own build pack for IBM Bluemix applications (or other Cloud Foundry based solutions), it is required to set the correct file mode for the executables before initially pushing them to GitHub. Otherwise the compilation will fail, and it seems to be a known bug for GitHub based repositories that the mode cannot be changed later.
The command for this is
git update-index --chmod=+x <path-to-file>
You can see the result when you commit the files to your respository:
> git commit -m "first commit" [master (root-commit) 680979a] first commit 4 files changed, 34 insertions(+) create mode 100644 README.md create mode 100755 bin/compile create mode 100755 bin/detect create mode 100755 bin/release
[The three files in the folder „/bin“ have the correct mode 755 instead 644]
You can find an example build pack here https://github.com/hasselbach/cf-buildpack-basic.git.