`--foo:bar:baz` in config.nims gives wrong results

[timotheecour]

Example 1

# main.nims:
# these work:
--define:"foo3: some def "
switch("hint", "msgOrigin")
switch("hint", "msgOrigin:off")
--hint:msgOrigin

# these don't work:
--define:foo1:bar1 # bug1
# --define:foo2=bar2 # bug2: Error: invalid command line option: '--foo2 = bar2'
# --hint:msgOrigin:off # bug4: Error: 'on' or 'off' expected, but 'msgOrigin:

# main.nim:
when true:
  const foo1 {.strdefine.} = ""
  const foo2 {.strdefine.} = ""
  const foo3 {.strdefine.} = ""
  echo (foo1, foo2, foo3)

nim r --define:foo2=bar2 main

Current Output

("\n bar1", "bar2", " some def ")

Expected Output

("bar1", "bar2", " some def ")

Example 2

likewise with other flags marked as these don't work:

Additional Information

1.5.1 3eebbb2
related recent PR: #16934 which fixed similar issues /cc @Clyybber