Revert to using cpuprofiler-0.0

We cannot publish sandboxfs as a crate if it depends on non-published
crates, so we must pin cpuprofiler to 0.0.  We were only using a custom
branch that simplifies the build process, but we can do the same thing
ourselves with a custom build.rs file.

Cargo.toml

@@ -18,6 +18,7 @@ default = []
 profiling = ["cpuprofiler"]
 
 [dependencies]
+cpuprofiler = { version = "0.0", optional = true }
 env_logger = "0.5"
 failure = "~0.1.2"
 getopts = "0.2"
@@ -29,12 +30,8 @@ serde_json = "1.0"
 signal-hook = "0.1"
 time = "0.1"
 
-[dependencies.cpuprofiler]
-# TODO(https://github.com/AtheMathmo/cpuprofiler/pull/10): Replace this with
-# 0.0.4 or an upstream branch reference once released.
-git = "https://github.com/jmmv/cpuprofiler.git"
-rev = "a852024d6aed7202863dc43a3348e793aa432d54"
-optional = true
+[build-dependencies]
+pkg-config = "0.3"
 
 [dependencies.fuse]
 # TODO(jmmv): Replace this with 0.4 once released.

build.rs

@@ -0,0 +1,47 @@
+// Copyright 2019 Google Inc.
+//
+// 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.
+
+extern crate pkg_config;
+
+/// Configures the crate to link against `lib_name`.
+///
+/// The library is searched via the pkg-config file provided in `pc_name`, which provides us
+/// accurate information on how to find the library to link to.
+///
+/// However, for libraries that do not provide a pkg-config file, `fallback` can be set to true to
+/// just rely on the linker's search path to find it.  This is not accurate but is better than just
+/// failing to build.
+#[allow(unused)]
+fn find_library(pc_name: &str, lib_name: &str, fallback: bool) {
+    match pkg_config::Config::new().atleast_version("2.0").probe(pc_name) {
+        Ok(_) => (),
+        Err(_) => if fallback { println!("cargo:rustc-link-lib={}", lib_name) },
+    };
+}
+
+fn main () {
+    // Look for the libraries required by our cpuprofiler dependency.  Such dependency should do
+    // this on its own but it doesn't yet.  Given that we just need this during linking, we can
+    // cheat and do it ourselves.
+    //
+    // Note that older versions of gperftools (the package providing libprofiler) did not ship a
+    // pkg-config file, so we must fall back to using the linker's path.
+    //
+    // TODO(https://github.com/AtheMathmo/cpuprofiler/pull/10): Remove this in favor of upstream
+    // doing the right thing when this PR is accepted a new cpuprofiler version is released.
+    // TODO(https://github.com/dignifiedquire/rust-gperftools/pull/1): Remove this in favor of
+    // upstream doing the right thing when this PR is accepted and switch to rust-gperftools instead
+    // (which has the added benefit of providing heap profiling).
+    #[cfg(feature = "profiling")] find_library("libprofiler", "profiler", true);
+}