[librsvg] CI: Do not fail if _build exists

[Jordan Petridis <jpetridis src gnome org>]

commit 45d90816ea24f84985c4425e78f0995080afeece
Author: Jordan Petridis <jordanpetridis protonmail com>
Date:   Mon Sep 10 22:53:49 2018 +0000

    CI: Do not fail if _build exists

 .gitlab-ci.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d3bf1132..126de8ee 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -41,7 +41,7 @@ stages:
   script:
     - rustc --version && cargo --version
     - |
-      mkdir _build
+      mkdir -p _build
       cd _build
       ../autogen.sh --enable-gtk-doc --enable-vala
       make
@@ -146,7 +146,7 @@ tarball:
   script:
     - rustc --version && cargo --version
     - |
-      mkdir _build
+      mkdir -p _build
       cd _build
       ../autogen.sh --enable-gtk-doc --enable-vala
       make distcheck DESTDIR=/tmp/distcheck