This partially revert commit 0ff00cca2a and should hopefully
fix bug #12647.
The issue is that the executable name in the Info.plist did not
match the name of the executable generated by Xcode (ScummVM vs
scummvm). I changed it back to $(EXECUTABLE_NAME), which is
automatically replaced by Xcode, and added a sed command to the
make target to replace it with the actual executable name (as
we did with the $(PRODUCT_BUNDLE_IDENTIFIER) already).
An alternative would be to hardcode the name to "scummvm" in the
Info.plist and change the iphonebundle and ios7bundle target to
also use all lower case scummvm when copying the executable.