Add automatic build of libcapnp if it's not detected

buildutils/build.py

@@ -0,0 +1,24 @@
+'Build the bundled capnp distribution'
+
+import subprocess
+import os
+import tempfile
+
+def build_libcapnp(bundle_dir, build_dir, verbose=False):
+  bundle_dir = os.path.abspath(bundle_dir)
+  capnp_dir = os.path.join(bundle_dir, 'capnproto-c++')
+  build_dir = os.path.abspath(build_dir)
+
+  with tempfile.TemporaryFile() as f:
+    stdout = f
+    if verbose:
+      stdout = None
+    conf = subprocess.Popen(['./configure', '--disable-shared', '--prefix', build_dir], cwd=capnp_dir, stdout=stdout)
+    returncode = conf.wait()
+    if returncode != 0:
+      raise RuntimeError('Configure failed')
+
+    make = subprocess.Popen(['make', '-j4', 'install'], cwd=capnp_dir, stdout=stdout)
+    returncode = make.wait()
+    if returncode != 0:
+      raise RuntimeError('Make failed')