cf. Homebrew/homebrew#28918.

Fixes Homebrew/homebrew#28901.

These methods are no longer required.

This reflects what Apple calls it in more recent versions of Xcode/OS X.

Since ae177adb2bd55ee5ad6367e7639c4cf0c774b63a, we can safely assume
that xcrun works, and a functioning xcrun will search dev_tools_path and
xctoolchain_path, so we can stop doing extra work here.

On CLT-only 10.7 and 10.8, xcrun will not work, but all the tools will
be in /usr/bin, which we check before invoking xcrun. Further, in this
case, dev_tools_path will be /usr/bin, and xctoolchain_path will not
exist, so the fallbacks here are unnecessary.

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

Closes Homebrew/homebrew#28878.

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

Closes Homebrew/homebrew#27813.

This is saved in HOMEBREW_OPTFLAGS and later mutated by
ENV.universal_binary, so if this returns nil the sub will fail.

In this case we need to handle the throwing on an exception when
attempting to initialize the gcc48 Formula object.

This initialization should be unnecessary if the core GCC is already
installed and rescued if not.

This code originated in a slightly different form in 8e88b22fd1ec65a344ce6e4facd6dad4b415b2ad:

https://github.com/Homebrew/homebrew/blob/8e88b22fd1ec65a344ce6e4facd6dad4b415b2ad/Library/Homebrew/extend/ENV.rb#L30-L32

Back then, MacOS.default_compiler could return nil, which meant
ENV.compiler could do the same. This code was carried forward as the
surrounding code changed. At this point it should be unreachable.

Formula::DATA only worked by accident of implementation; DATA during the
build is actually Object::DATA, so we should mirror that here.

This reverts commit b12444ba6e1ac1d596a70ff4c777d9386d0791ac.

Instances of `IOPatch` created by `patch :DATA` are not affected by re-setting
the `DATA` constant of the `Formula` instance. For these patches, we iterate
through the `patchlist` and use `instance_variable_set` to attach data.

A bit hacky, but `patchlist` has no write accessors so there isn't a clean way
to modify patch contents.

Closes Homebrew/homebrew#28820.

On older Apple compilers "-O4" is known to cause build errors. On recent
clang, it's the same as "-O3" and you have to pass "-O3 -flto" to get
the old behavior.

With --multiple, only list formulae with multiple versions installed.

Closes Homebrew/homebrew#28717.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

This matches the logic in find_formula.