Simplifying patch-builder use in builder container

To make easier for the user to utilize the patch-builder tool we
made 3 different changes:
- stx-builder.Dockerfile: Add python modules to be installed when
building the image.
- buildrc: Add /stx/patch to $PATCH env variable, making "patch-builder"
script more easy execute.
- userenv: Update information in the "welcome" message for builder
container.

Test plan:
    PASS: Rebuild all containers, using:
        "./stx-init-env --rebuild"
    PASS: Test usual build process, using:
        "downloader"
        "build-pkgs"
        "build-image"
    PASS: Test patch builder, using:
	"patch-builder --recipe <path>"

Story: 2010676
Task: 50438

Change-Id: Ic458f58d376a64d3654c6f19e5d11d0e99f8d6f9
Signed-off-by: Dostoievski Batista <dostoievski.albinobatista@windriver.com>

stx/dockerfiles/stx-builder.Dockerfile

@@ -81,7 +81,10 @@ RUN pip3 --no-cache-dir install \
         pulp_deb_client \
         pulp_file_client \
         progressbar \
-        git+https://github.com/masselstine/aptly-api-client.git
+        git+https://github.com/masselstine/aptly-api-client.git \
+        click \
+        lxml \
+        pycryptodomex
 
 # Misc files
 RUN sed -i '/^proxy_dns*/d' /etc/proxychains.conf && \

stx/toCOPY/builder/buildrc

@@ -33,8 +33,9 @@ export STX_CONFIG_DIR=$MY_REPO_ROOT_DIR/stx-tools
 export PREFIX_BINARYLIST_DIR=debian-mirror-tools/config/debian/
 export STX_BINARYLIST_DIR=$STX_CONFIG_DIR/$PREFIX_BINARYLIST_DIR
 export STX_GIT_SRC_DIR=$MY_REPO/stx/git
+export PATCH_BUILDER_PATH=$MY_REPO/build-tools/stx/patch
 
-export PATH=$PATH:$MY_BUILD_TOOLS_DIR/stx:/opt/LAT/lat
+export PATH=$PATH:$MY_BUILD_TOOLS_DIR/stx:/opt/LAT/lat:$PATCH_BUILDER_PATH
 export PYTHONPATH=$PYTHONPATH:$MY_BUILD_TOOLS_DIR/stx
 
 export STX_MIRROR=/import/mirrors/starlingx

stx/toCOPY/builder/userenv

@@ -50,6 +50,8 @@ To clean and re-build all packages:
 To make image (std and rt kernels are included):
     build-image
 
+To build patches:
+    patch-builder --recipe <path to recipe>
 EOF
 fi
 cd ${MY_WORKSPACE}