ci: Set the PATH var in the docker image rather than scripts

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1084>

ci/images_template.yml

@@ -1,4 +1,4 @@
 variables:
-  GST_RS_IMG_TAG: '2022-08-23.0'
+  GST_RS_IMG_TAG: '2022-08-23.2'
   GST_RS_STABLE: '1.63.0'
   GST_RS_MSRV: '1.60.0'

ci/run_windows_tests.ps1

@@ -1,7 +1,3 @@
-# Add the precompiled gst binaries to the path
-$env:Path += ';C:/gst-install/bin\'
-$env:PKG_CONFIG_PATH = "C:/gst-install/lib/pkgconfig"
-
 # List of all the crates we want to build
 # We need to do this manually to avoid trying
 # to build egl,wayland,x11 etc, which can't

ci/windows-docker/Dockerfile

@@ -10,6 +10,9 @@ ARG DEFAULT_BRANCH="main"
 ARG RUST_VERSION="invalid"
 
 RUN choco install -y pkgconfiglite
+
+# https://stackoverflow.com/a/50716450
+RUN setx PATH '%PATH%;C:\gst-install\bin'
 ENV PKG_CONFIG_PATH="C:\gst-install\lib\pkgconfig"
 
 COPY install_gst.ps1 install_gtk.ps1 C:\

ci/windows-docker/install_gtk.ps1

@@ -1,7 +1,5 @@
 [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12;
 
-$env:Path += ";C:\gst-install\bin\"
-
 # Download gstreamer and all its subprojects
 git clone -b gtk-4-6 --depth 1 https://gitlab.gnome.org/gnome/gtk.git C:\gtk
 if (!$?) {