The idea here is to prevent future builds from calling dsymutil
if the native executable hasn't changed since the previous build.
The reason we need to touch the dSYM Info.plist after stripping
is because the SymbolStrip task *may* modify the native executable
thereby giving it a newer mtime timestamp than the dSYM Info.plist
which would cause later builds to re-run the dsymutil task on an
already-stripped native executable.
It should be noted, however, that the _CodesignAppBundle target
already updates the mtime timestamp of the dSYM Info.plist for
precisely the same reason and since it is run *after* the
_GenerateDebugSymbols target, the 'touch' should generally not
be needed in the _GenerateDebugSymbols target.
Rolf Bjarne Kvinge
Jeffrey Stedfast