[pitivi] build: Create the build dir only when missing

[Alexandru Băluț <alexbalut src gnome org>]

commit 23c05efddd07cc2abe4047a6678a9fab5562d498
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Sun Aug 13 19:58:48 2017 +0200

    build: Create the build dir only when missing
    
    This logic was part of the configure script removed in
    05b3aee5ffded84d2c7d4a7f9e2dca4eda8942ef

 build/flatpak/pitivi-flatpak |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)
---
diff --git a/build/flatpak/pitivi-flatpak b/build/flatpak/pitivi-flatpak
index f1c34d7..8184b08 100755
--- a/build/flatpak/pitivi-flatpak
+++ b/build/flatpak/pitivi-flatpak
@@ -527,11 +527,15 @@ class PitiviFlatpak:  # pylint: disable=too-many-instance-attributes
                 self.exit(1)
             subprocess.check_call(builder_args, cwd=self.scriptdir)
 
-            meson_args = ["meson", "mesonbuild/", "--prefix=/app",
-                          "--libdir=lib", "-Ddisable_gtkdoc=true",
-                          "-Ddisable_doc=true"]
-            self.run_in_sandbox(*meson_args, exit_on_failure=True,
-                                cwd=self.topdir)
+            if not os.path.isdir("mesonbuild/"):
+                # Create the build directory.
+                meson_args = ["meson", "mesonbuild/", "--prefix=/app",
+                              "--libdir=lib", "-Ddisable_gtkdoc=true",
+                              "-Ddisable_doc=true"]
+                self.run_in_sandbox(*meson_args, exit_on_failure=True,
+                                    cwd=self.topdir)
+
+            # Build the buildable parts of Pitivi.
             ninja_args = ["ninja", "-C", "mesonbuild/"]
             self.run_in_sandbox(*ninja_args, exit_on_failure=True,
                                 cwd=self.topdir)