Install required clang-11 and llvm-11. (#451)

Fix PostGIS image with install specified `clang-11` and `llvm-11` 

Update to new `docker compose` for running tests.
 - code taken from openmaptiles/openmaptiles#1497 (thanks @wcedmisten)

Makefile

@@ -16,6 +16,16 @@ DOCKER_OPTS  ?= -i --rm -u $$(id -u $${USER}):$$(id -g $${USER})
 # Optionally pass in extra parameters to the docker build command
 DOCKER_BUILD_EXTRAS ?=
 
+# https://github.com/openmaptiles/openmaptiles/pull/1497
+# Support newer `docker compose` syntax in addition to `docker-compose`
+ifeq (, $(shell which docker-compose))
+  DOCKER_COMPOSE_COMMAND := docker compose
+  $(info Using docker compose V2 (docker compose))
+else
+  DOCKER_COMPOSE_COMMAND := docker-compose
+  $(info Using docker compose V1 (docker-compose))
+endif
+
 ifneq ($(strip $(NO_REFRESH)),)
   $(info Skipping docker image refresh)
 else
@@ -108,9 +118,9 @@ build-sql-tests: prepare build-docker
 	@echo ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"
 	@echo "   Running Postgres SQL tests"
 	@echo ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"
-	docker-compose --file tests/sql/docker-compose.yml rm -f && \
-	timeout 180 docker-compose --file tests/sql/docker-compose.yml up --abort-on-container-exit && \
-	docker-compose --file tests/sql/docker-compose.yml rm -f
+	$(DOCKER_COMPOSE_COMMAND) --file tests/sql/docker-compose.yml rm -f && \
+	$(DOCKER_COMPOSE_COMMAND) --file tests/sql/docker-compose.yml up --abort-on-container-exit --wait-timeout 180 && \
+	$(DOCKER_COMPOSE_COMMAND) --file tests/sql/docker-compose.yml rm -f
 
 .PHONY: build-bin-tests
 build-bin-tests: prepare build-docker

docker/postgis/Dockerfile

@@ -34,6 +34,8 @@ RUN set -eux  ;\
         postgresql-server-dev-$PG_MAJOR \
         libkakasi2-dev \
         libgdal-dev \
+        clang-11 \
+        llvm-11 \
     ;\
     ## Install specific GEOS version
     #cd /opt/  ;\
@@ -50,8 +52,6 @@ RUN set -eux  ;\
     cd /opt/  ;\
     git clone --quiet --depth 1 -b $PGSQL_GZIP_TAG $PGSQL_GZIP_REPO  ;\
     cd pgsql-gzip  ;\
-    ln -s /usr/bin/clang-13 /usr/bin/clang-11  ;\
-    ln -s /usr/lib/llvm-13 /usr/lib/llvm-11  ;\
     make  ;\
     make install  ;\
     rm -rf /opt/pgsql-gzip  ;\