Fix extra spaces and colons in flags and environment variables

[klimkin]

According to Bash expansion:

${parameter:+word}

Correct form for PATH:

${PATH:+:$PATH}

Correct form for CFLAGS:

${CFLAGS:+ $CFLAGS}

Fixes #8495

Changelog: Fix: Remove extra spaces in flags and colons in path variables.
Docs: omit

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[klimkin]

@jgsogo, @memsharded FYI

[memsharded]

Thanks for contributing this @klimkin

I am a bit surprised that our tests didn't catch such bug. I am experimenting with a new way to handle the environment in #8426, and I haven't been able to reproduce, it seems that modern bash can process the expansion correctly without the :.

I think this is most likely good to be merged, if it is the "canonical" way, but it would be great to have also first a failing test that proves that the current expansion without ":" doesn't work as intended. Could you please try to contribute such a test, or give some hints about the failures that could happen if the ":" is missing?

[klimkin]

Added unit-test: e64fee7

@memsharded Here is a nice write-up: https://tldp.org/LDP/abs/html/parameter-substitution.html

{parameter+alt_value}, ${parameter:+alt_value}
If parameter set, use alt_value, else use null string.

Both forms nearly equivalent. The : makes a difference only when parameter has been declared and is null, see below.

param=

a=${param+xyz}
echo "a = $a"      # a = xyz

a=${param:+xyz}
echo "a = $a"      # a =
# Different result from   a=${param5+xyz}

[jgsogo]

Love to see all those FIXME being actually fixed! 💯