tools/bazel: Split environment into separate script.

This splits the initialization of build environment into a separate
build_env.sh script, allowing for more complex control flow than when
setting everything up in a single `env -i` invocation, and allowing
the environment variables to sourced by other, non-bazel scripts.

Signed-off-by: format 20.02.05 <github.com/ChrisCummins/format>

tools/bazel

@@ -10,63 +10,10 @@
 # environments such as terminals, IDEs, editors, etc.  This is especially
 # frustrating as it invalidates the results of (possibly expensive) test runs.
 #
-# This bazel wrapper script forwards only the minimum environment variables
-# required for bazel to complete it's task: a ${TERM} environment (so it knows
-# how to format build output), and a ${PATH} which has the necessary tools
-# required to complete the build (e.g. the compiler toolchains and python
-# runtimes).
-#
-# This assumes that /bin, /usr/bin, and /usr/local/bin contain the necessary
-# build tools, which is true for the standard Linux / macOS environments I use.
-# Your mileage may vary.
-set -eu
-
-build_path() {
-    local _dir=""
-    local _path=""
-
-    for _dir in "$@"
-    do
-        if [ -d $_dir ]; then
-            _path=$_path:$_dir
-        fi
-    done
-
-    _path=${_path:1}
-    echo $_path
-}
-
-# Accepts an array of directories and returns a colon separated path
-# of all of the directories that exist, in order.  Example usage:
-#
-#    dirs=("/usr/local/bin" /usr/bin "/not a real path")
-#    unset FOO
-#    FOO=$(build_path "${dirs[@]}")
-#    echo $FOO
-#    # Outputs: /usr/local/bin:/usr/bin
-path_dirs=( \
-    /usr/local/opt/llvm/bin \
-    /usr/local/opt/gnu-sed/libexec/gnubin \
-    /usr/bin \
-    /usr/local/bin \
-    /bin \
-)
-
-if [[ -f "/usr/local/opt/llvm/bin/clang" ]]; then
-  CC=/usr/local/opt/llvm/bin/clang
-  CXX=/usr/local/opt/llvm/bin/clang++
-else
-  CC="$(which gcc)"
-  CXX="$(which g++)"
-fi
-
-# PULLET_TIMEOUT to increase the timeout on docker image pulls from the default
-# 600s. See: https://github.com/bazelbuild/rules_docker
-set +u
-env -i \
-  TERM="$TERM" \
-  PATH="$(build_path ${path_dirs[@]})" \
-  CC=$CC \
-  CXX=$CXX \
-  PULLER_TIMEOUT=3600 \
-  "$BAZEL_REAL" "$@"
+# Instead, the goal of this script is to create consistent environment which
+# can be run from anywhere and always makes sure that bazel gets the same
+# variables to work with. The way of achieving that is to start from a blank
+# slate empty environment and call a script which sets up the necessary
+# variables.
+set -e
+env -i TERM="$TERM" HOME="$HOME" tools/bazel_env.sh "$BAZEL_REAL" "$@"

tools/bazel_env.sh

@@ -0,0 +1,63 @@
+#!/usr/bin/env bash
+#
+# This script exports the environment variables which are used for bazel
+# invocations. Use it as a wrapper around a bazel invocation, optionally
+# using `exec -i` to produce a clean environment:
+#
+#     $ exec -i tools/bazel_env.sh bazel build //...
+#
+# This script assumes that /bin, /usr/bin, and /usr/local/bin contain the
+# necessary build tools, which is true for the standard Linux / macOS
+# environments I use. Your mileage may vary.
+set -eu
+
+# Accepts an array of directories and returns a colon separated path
+# of all of the directories that exist, in order.  Example usage:
+#
+#    dirs=("/usr/local/bin" /usr/bin "/not a real path")
+#    unset FOO
+#    FOO=$(build_path "${dirs[@]}")
+#    echo $FOO
+#    # Outputs: /usr/local/bin:/usr/bin
+build_path() {
+  local _dir=""
+  local _path=""
+
+  for _dir in "$@"; do
+    if [ -d $_dir ]; then
+      _path=$_path:$_dir
+    fi
+  done
+
+  _path=${_path:1}
+  echo $_path
+}
+
+# Build our path.
+path_dirs=(
+  /usr/local/opt/llvm/bin
+  /usr/local/opt/gnu-sed/libexec/gnubin
+  /Library/TeX/Distributions/.DefaultTeX/Contents/Programs/texbin
+  /usr/bin
+  /usr/local/bin
+  /bin
+)
+export PATH="$(build_path ${path_dirs[@]})"
+
+# Note(github.com/ChrisCummins/phd/issues/55): On macOS, custom LDFLAGS and
+# CPPFLAGS are required to pip build MySQLdb:
+if [[ -d /usr/local/opt/openssl ]]; then
+  export LDFLAGS="-L/usr/local/opt/openssl/lib"
+  export CPPFLAGS="-I/usr/local/opt/openssl/include"
+fi
+
+# Increase the timeout on docker image pulls from the default 600s.
+# See: https://github.com/bazelbuild/rules_docker
+export PULLER_TIMEOUT=3600
+
+if [[ -f "/usr/local/opt/llvm/bin/clang" ]]; then
+  export CC=/usr/local/opt/llvm/bin/clang
+  export CXX=/usr/local/opt/llvm/bin/clang++
+fi
+
+$@