Reuse more code to avoid errors due to duplication.

Fix #3883
Revert 2fb5ead3

Requirement#modify_build_environment may depend on the side effects of
Requirement#satisfied?, so make sure the latter is called at least once
for each requirement during formula installation. Prior to b70b5429,
Requirement#satisfied? would usually be called during Build#expand_reqs,
but that is longer the case.

This has been a nightmare in terms of the complexity to our dependency
system and the whack-a-mole required on bugs. If a Requirement resolves
to a Formula it should just use `depends_on "formula"` instead. This
matches the effective behaviour all users of bottles (the vast majority
of users and installs) and what we're doing in Homebrew/homebrew-core.

so that it includes the commit.

These can be useful for later inspection or upload by `gist-logs` if
there's a failed install and it's unclear from logs alone what options
were used.

See discussion in Homebrew/brew#800.

The experiment to add `-no_weak_imports` unconditionally has been a bit
of a failure. It's broken more than it's fixed and I don't think we can
have this as a default for Xcode 8.

Add `ENV.no_weak_imports` to be used by formulae authors and make
`ENV.no_weak_imports a no-op (for now).

We may reconsider this behaviour in future.

Go makes extensive use of weak imports so we need to allow them when
building Go-using software.

Closes https://github.com/Homebrew/homebrew-core/issues/4047.

The `build` and `source_modified_time` arguments are always coming from
the matching attributes of the `Formula` instance. Thus query `formula`
for them instead of passing them individually.

Also enables sandbox for --interactive and --debug use of install
and test, using automatic retention.

Closes #66.

Signed-off-by: Andrew Janke <andrew@apjanke.net>

This came up in https://github.com/Homebrew/homebrew-emacs/pull/158#issuecomment-172031003;  `install_metafiles` is passed the current directory, which can be changed during installation by `Dir.chdir`.

There may be cases where the metafiles are in a subdirectory, but my
guess is those are rare and this is brittle and undocumented behavior
anyway.

sudo -k cannot be used inside sandbox

Closes Homebrew/homebrew#43345.

Signed-off-by: Xu Cheng <xucheng@me.com>

Closes Homebrew/homebrew#42354.

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

I want to decouple from the global ENV constant as much as possible so
that eventually we can change the build environment implementation.
detect_stdlibs only cares about the compiler, not the whole ENV.

Dependency is another similar, related class and it's super confusing
to have some Requirements that are named *Dependency.

Closes Homebrew/homebrew#38891.

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

This is a more standard way to pass fd in UNIX world.
At the same time, it helps to remove a few hacks and
simplifies the code in the sandbox.

Closes Homebrew/homebrew#38434.

Signed-off-by: Xu Cheng <xucheng@me.com>

This is a follow-up of Homebrew/homebrew#37734. I think we should treat `install_metafiles` as
a general issue rather than a formula-specific one.

Closes Homebrew/homebrew#37968.

Signed-off-by: Xu Cheng <xucheng@me.com>