gitlab-ci: Switch the meson-main build type to debugoptimized.

Now that we're running the drivers we build, building with
optimization is important for keeping our runtime down.  Shaves about
4 minutes of runtime off of GLES2 CTS of llvmpipe at 64x64.

v2: Only switch meson-main until we enable CTS for other builds
    on request by Michel.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

.gitlab-ci.yml

@@ -175,6 +175,7 @@ meson-main:
       -D osmesa=gallium
       -D tools=all
     MESON_SHADERDB: "true"
+    BUILDTYPE: "debugoptimized"
 
 meson-clover:
   extends: .meson-build

.gitlab-ci/meson-build.sh

@@ -19,7 +19,7 @@ meson _build --native-file=native.file \
       ${CROSS+--cross /cross_file-$CROSS.txt} \
       -D prefix=`pwd`/install \
       -D libdir=lib \
-      -D buildtype=debug \
+      -D buildtype=${BUILDTYPE:-debug} \
       -D build-tests=true \
       -D libunwind=${UNWIND} \
       ${DRI_LOADERS} \