(folly) osx bootstrap script

Summary:
This is a bootstrap script for building folly on osx. I attempted to make it Just Work™ for anyone who uses Homebrew (http://brew.sh/) but even if it doesn't work out of the box it should be instructive for the motivated developer on OSX.

Facebook:
In #5134151 Wangle used to not build, because something was using a futex. But that seems to have been rectified (or the build problems are hiding in headers that aren't used in the libfolly build).

I'll also update https://our.intern.facebook.com/intern/wiki/Folly/BuildingOnMac to point people to this script instead.

Test Plan:
Tested on my laptop which is running Yosemite (10.10.1)
Build, then inspect `otool -L .libs/*dylib`

Reviewed By: davejwatson@fb.com

Subscribers: folly-diffs@, exa

FB internal diff: D1765248

Tasks: 5134151

Signature: t1:1765248:1420500905:bc5da97a0446f502cb2badc85c9004ff0a62027a

diff --git a/folly/bootstrap-osx-homebrew.sh b/folly/bootstrap-osx-homebrew.sh
new file mode 100755 (executable)
index 0000000..6565f4b
--- /dev/null
+++ b/folly/bootstrap-osx-homebrew.sh
@@ -0,0 +1,37 @@
+#!/bin/bash -x
+# The only prerequisite should be homebrew. If something doesn't work out of
+# the box with just homebrew, let's fix it.
+
+# fail fast
+set -e
+
+brewget() {
+    brew install $@ || brew upgrade $@
+}
+
+# tool dependencies: autotools, scons (for double-conversion), and gcc 4.9
+brewget autoconf automake libtool scons gcc
+
+# dependencies
+brewget glog gflags boost libevent
+
+# Install the double-conversion library.
+# NB their install target installs the libs but not the headers, hence the
+# CPPFLAGS and link shenanigans.
+DOUBLE_CONVERSION_CPPFLAGS="-I./double-conversion/src"
+test -d double-conversion || {
+    git clone https://github.com/floitsch/double-conversion.git
+    pushd double-conversion/src
+    ln -s . double-conversion
+    popd
+}
+pushd double-conversion
+scons
+# fool libtool into using static linkage
+# (this won't work if you've already installed libdouble-conversion into a
+# default search path)
+rm -f libdouble-conversion*dylib
+popd
+
+autoreconf -i
+./configure CPPFLAGS="-I./double-conversion/src" LDFLAGS="-L./double-conversion" CXX=g++-4.9