The array elements here are individual arguments to exec, not a string
to pass to the shell; this only appeared to work. In reality, `opam
list` accepts "|" as valid argument, and the command works fine without
grepping the output.

Fixes Homebrew/homebrew#25779.

Closes Homebrew/homebrew#25706.
Closes Homebrew/homebrew#25682.

This reverts commit 1cd636d368c66d1346adc1c38633c8f204c759f4.

Closes Homebrew/homebrew#25709.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Fixes Homebrew/homebrew#25546.

This raise happened in no other ENV methods, and isn't really necessary
since fails_with guards against this method actually being called unless
gcc-4.2 is actually installed.

This reverts commit 0e1d52c0d3945ae0ac69383c7734e425b7fbf8f1.

This reverts commit 8ec6123d439e8f4d3586bbca6a426b726bd5e9dd.

This reverts commit bedcbb806bb8a991a1317b4ccde8d16b6974cc46.

This reverts commit f4dc5614953b3b90acc28c83262d56587b0616b1.

Since ENV.cc/cxx are accessors to ENV, any values being passed through
are coerced into strings, which means that a nil `ENV.cc` is actually
an empty string - which isn't considered to be false in Ruby.

Fixes mistydemeo/tigerbrew#161.
Fixes mistydemeo/tigerbrew#135.

Just make it a warning instead.

Closes Homebrew/homebrew#25511.
Closes Homebrew/homebrew#25617.

Closes Homebrew/homebrew#20482.

This can happen on e.g. fossil where the dependency HEAD requires having
an install of fossil in order to check it out. Bit of a silly edge case
but this handles it.

Fixes Homebrew/homebrew#25605

Fixes Homebrew/homebrew#25561.
Fixes Homebrew/homebrew#25410.

Solely because I think `ENV.deparallelize` is *way* clearer than
`ENV.j1`, at least to the uninitiated.

Also, updating the template will reduce the number of `ENV.j1`s that
persist because the Homebrew maintainers want clean histories of
formulae. Ideally, this change should prevent any more cases from being
introduced!

Closes Homebrew/homebrew#25431.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>