add a top-level build.sh to build folly via getdeps.py

Summary:
Add a small top-level build.sh script that invokes
build/fbcode_builder/getdeps.py to perform the build.  This primarily helps
make the getdeps build process more discoverable to users.

Also document this script in README.md

Reviewed By: yfeldblum

Differential Revision: D23484822

fbshipit-source-id: 6013ace6d80d7d3d80aa87d4c6269ac106814cf0

.projectid

+folly

README.md

@@ -72,6 +72,33 @@ Folly is published on GitHub at https://github.com/facebook/folly
 
 ### Build Notes
 
+Because folly does not provide any ABI compatibility guarantees from commit to
+commit, we generally recommend building folly as a static library.
+
+#### build.sh
+
+The simplest way to build folly is using the `build.sh` script in the top-level
+of the repository.  `build.sh` can be used on Linux and MacOS, on Windows use
+the `build.bat` script instead.
+
+This script will download and build all of the necessary dependencies first,
+and will then build folly.  This will help ensure that you build with recent
+versions of all of the dependent libraries, regardless of what versions are
+installed locally on your system.
+
+By default this script will build and install folly and its dependencies in a
+scratch directory.  You can also specify a `--scratch-path` argument to control
+the location of the scratch directory used for the build.  There are also
+`--install-dir` and `--install-prefix` arguments to provide some more
+fine-grained control of the installation directories.  However, given that
+folly provides no compatibility guarantees between commits we generally
+recommend building and installing the libraries to a temporary location, and
+then pointing your project's build at this temporary location, rather than
+installing folly in the traditional system installation directories.  e.g., if
+you are building with CMake you can use the `CMAKE_PREFIX_PATH` variable to
+allow CMake to find folly in this temporary installation directory when
+building your project.
+
 #### Dependencies
 
 folly supports gcc (5.1+), clang, or MSVC. It should run on Linux (x86-32,

build.bat

+@REM Copyright (c) Facebook, Inc. and its affiliates.
+@REM
+@REM Licensed under the Apache License, Version 2.0 (the "License");
+@REM you may not use this file except in compliance with the License.
+@REM You may obtain a copy of the License at
+@REM
+@REM     http://www.apache.org/licenses/LICENSE-2.0
+@REM
+@REM Unless required by applicable law or agreed to in writing, software
+@REM distributed under the License is distributed on an "AS IS" BASIS,
+@REM WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@REM See the License for the specific language governing permissions and
+@REM limitations under the License.
+
+@echo off
+SETLOCAL
+if exist %~dp0\..\..\opensource\fbcode_builder\getdeps.py (
+  set GETDEPS=%~dp0\..\..\opensource\fbcode_builder\getdeps.py
+) else if exist %~dp0\build\fbcode_builder\getdeps.py (
+  set GETDEPS=%~dp0\build\fbcode_builder\getdeps.py
+) else (
+  echo "error: unable to find getdeps.py"
+  exit 1
+)
+
+python3.exe %GETDEPS% build folly %*

build.sh

+#!/bin/bash
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This script is just a simple wrapper around the
+# build/fbcode_builder/getdeps.py script.
+#
+# Feel free to invoke getdeps.py directly to have more control over the build.
+
+SCRIPT_DIR=$(dirname "${BASH_SOURCE[0]}")
+GETDEPS_PATHS=(
+    "$SCRIPT_DIR/build/fbcode_builder/getdeps.py"
+    "$SCRIPT_DIR/../../opensource/fbcode_builder/getdeps.py"
+)
+for getdeps in "${GETDEPS_PATHS[@]}"; do
+    if [[ -x "$getdeps" ]]; then
+        exec "$getdeps" build folly "$@"
+    fi
+done
+echo "Could not find getdeps.py" >&2
+exit 1