Give CMake a timeout for when it hangs

In Debian Jessie, CMake will sometimes fail to correctly wait for the programs
it has spawned. While a proper fix would be in CMake itself, protect ourselves
from this by giving it a generous but limited time in which to run.

When it hangs, it will now instead be killed by the build process and we can try
again, instead of having to hunt down processes across machines.

Author: carlosmn

ext/rugged/extconf.rb

@@ -4,6 +4,7 @@
 # For full terms see the included LICENSE file.
 
 require 'mkmf'
+require 'timeout'
 
 RbConfig::MAKEFILE_CONFIG['CC'] = ENV['CC'] if ENV['CC']
 
@@ -23,6 +24,26 @@ def sys(cmd)
   ret
 end
 
+# Thrown when we detect CMake is taking too long and we killed it
+class CMakeTimeout < StandardError
+end
+
+def self.run_cmake(timeout, args)
+  # Set to process group so we can kill it and its children
+  pid = Process.spawn("cmake #{args}", pgroup: true)
+
+  Timeout.timeout(timeout) do
+    Process.waitpid(pid)
+  end
+
+rescue Timeout::Error
+  # Kill it, #detach is essentially a background wait, since we don't actually
+  # care about waiting for it now
+  Process.kill(-9, pid)
+  Process.detach(pid)
+  raise CMakeTimeout.new("cmake has exceeded its timeout of #{timeout}s")
+end
+
 MAKE = if Gem.win_platform?
   # On Windows, Ruby-DevKit only has 'make'.
   find_executable('make')
@@ -80,7 +101,7 @@ def sys(cmd)
     Dir.chdir("build") do
       # On Windows, Ruby-DevKit is MSYS-based, so ensure to use MSYS Makefiles.
       generator = "-G \"MSYS Makefiles\"" if Gem.win_platform?
-      sys("cmake .. -DBUILD_CLAR=OFF -DTHREADSAFE=ON -DBUILD_SHARED_LIBS=OFF -DCMAKE_C_FLAGS=-fPIC -DCMAKE_BUILD_TYPE=RelWithDebInfo #{cmake_flags.join(' ')} #{generator}")
+      run_cmake(5 * 60, ".. -DBUILD_CLAR=OFF -DTHREADSAFE=ON -DBUILD_SHARED_LIBS=OFF -DCMAKE_C_FLAGS=-fPIC -DCMAKE_BUILD_TYPE=RelWithDebInfo #{cmake_flags.join(' ')} #{generator}")
       sys(MAKE)
 
       # "normal" libraries (and libgit2 builds) get all these when they build but we're doing it