Docker: Added oportunity to set build flags (some envs) via docker bu…

…ild args

Dockerfile

@@ -7,6 +7,11 @@ ARG DEBIAN_FRONTEND=noninteractive
 ARG USER_NAME=ardupilot
 ARG USER_UID=1000
 ARG USER_GID=1000
+ARG SKIP_AP_EXT_ENV=1
+ARG SKIP_AP_GRAPHIC_ENV=1
+ARG SKIP_AP_COV_ENV=1
+ARG SKIP_AP_GIT_CHECK=1
+
 RUN groupadd ${USER_NAME} --gid ${USER_GID}\
     && useradd -l -m ${USER_NAME} -u ${USER_UID} -g ${USER_GID} -s /bin/bash
 
@@ -29,7 +34,7 @@ RUN chown -R ${USER_NAME}:${USER_NAME} /${USER_NAME}
 
 USER ${USER_NAME}
 
-ENV SKIP_AP_EXT_ENV=1 SKIP_AP_GRAPHIC_ENV=1 SKIP_AP_COV_ENV=1 SKIP_AP_GIT_CHECK=1
+ENV SKIP_AP_EXT_ENV=$SKIP_AP_EXT_ENV SKIP_AP_GRAPHIC_ENV=$SKIP_AP_GRAPHIC_ENV SKIP_AP_COV_ENV=$SKIP_AP_COV_ENV SKIP_AP_GIT_CHECK=$SKIP_AP_GIT_CHECK
 RUN Tools/environment_install/install-prereqs-ubuntu.sh -y
 
 # add waf alias to ardupilot waf to .ardupilot_env