shims/super/cc: remove isysroot space to fix cpp

[Bo98]

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---

This is a fix to #5153, where the cpp shim was broken in Xcode 10 and later.

It turns out that Xcode's cpp is just a dumb script. Here's a snippet from it:

while [ $# -gt 0 ]
do
        A="$1"
        shift

        case "$A" in
        -nostdinc)
                NSI=yes
                ;;
        -traditional)
                ;;
        -I*)
                INCS=("${INCS[@]}" "$A")
                ;;
        -imacros|-include|-idirafter|-iprefix|-iwithprefix)
                INCS=("${INCS[@]}" "$A" "$1")
                shift
                ;;
        -*)
                OPTS=("${OPTS[@]}" "$A")
                ;;
        *)
                FOUNDFILES=yes
                # If we've found an input name and there's still an arg left,
                # that next arg will be the output file.
                if [ $# -eq 1 ]; then
                    OUTPUT="$1"
                    # and get rid of last arg
                    shift
                fi
                $CPP -traditional "${INCS[@]}" -x c "${OPTS[@]}" "$A" \
                     -o "$OUTPUT" || exit $?
                ;;
        esac
done

It splits arguments by spaces, and completely breaks down when we pass -isysroot sdk. The entire flow revolves around $#, $1 and shift which work by splitting by spaces so sees -isysroot and sdk as separate arguments. Here is a demonstration of what happens:

$ cpp -isysroot/A -isysroot/B test.ext
xcrun cc -E -traditional  -x c  -isysroot/A -isysroot/B test.ext -o -

$ cpp -isysroot /A -isysroot /B test.ext
xcrun cc -E -traditional  -x c  -isysroot /A -o -
xcrun cc -E -traditional  -x c  -isysroot -isysroot /B test.ext -o -

The script does have special handling for -imacros, -include, -idirafter, -iprefix and -iwithprefix to work with spaces (or rather require spaces), but not -isysroot.

When interacting with clang directly, -isysroot works both with and without spaces between -isysroot and the path. In fact, originally spaces weren't supported there either - that's a later innovation. MacPorts doesn't put a space after -isysroot for that reason, albeit that older toolchain support isn't a concern in Homebrew.

Considering -isysroot without spaces still works today, I propose removing the space as that fixes all the problems without having to do special cpp handling. Note that -isystem already behaves this way.

[maxim-belkin]

👍

-isysroot sdk is processed by the -*) option above. Therefore, one has to escape spaces between words that are part of the same "option" as is the case with -isysroot sdk. In the current syntax, both -isysroot and sdk are provided to cpp as separate words and, therefore, processed by cpp individually. So, unless there is more to it, the "fix" can still have a space between -isysroot and sdk, but these words have to be part of the same "option":

args << "-isysroot #{sysroot}"

[Bo98]

Indeed that should also work. Ruby will handle the rest.

[MikeMcQuaid]

Works for me, thanks @Bo98 for another great PR!