update drone.yml to install a system dune

Make SYS_DUNE_BASE_DIR configurable

.drone.yml

@@ -11,6 +11,8 @@ steps:
   commands:
   - sudo apt-get update && sudo apt-get -y install libgmp-dev m4 libdw-dev
   - sudo chown -R opam .
+  - eval $(opam env)
+  - opam install dune
   - export ITER=1
   - export OPAM_DISABLE_SANDBOXING=true
   - make ocaml-versions/4.07.1.bench
@@ -19,6 +21,8 @@ steps:
   commands:
   - sudo apt-get update && sudo apt-get -y install libgmp-dev m4 libdw-dev
   - sudo chown -R opam .
+  - eval $(opam env)
+  - opam install dune
   - export ITER=1
   - export OPAM_DISABLE_SANDBOXING=true
   - export BENCH_TARGET=parallelbench
@@ -28,6 +32,8 @@ steps:
   commands:
   - sudo apt-get update && sudo apt-get -y install libgmp-dev m4 libdw-dev
   - sudo chown -R opam .
+  - eval $(opam env)
+  - opam install dune
   - export ITER=1
   - export OPAM_DISABLE_SANDBOXING=true
   - export BENCH_TARGET=multibench

Makefile

@@ -35,12 +35,13 @@ export OPAMROOT=$(CURDIR)/_opam
 # HACK: we are using the system installed dune to avoid breakages with
 # multicore and 4.09/trunk
 # This is a workaround for r14/4.09/trunk until better solutions arrive
-SYS_DUNE_BASE_DIR = $(subst /bin/dune,,$(shell which dune))
+SYS_DUNE_BASE_DIR ?= $(subst /bin/dune,,$(shell which dune))
 
 setup_sys_dune:
 ifeq (,$(SYS_DUNE_BASE_DIR))
 	$(error Could not find a system installation of dune (try `opam install dune`?))
 else
+	@echo "Linking to system dune files found at: "$(SYS_DUNE_BASE_DIR)
 	rm -rf $(CURDIR)/_opam/sys_dune
 	mkdir -p $(CURDIR)/_opam/sys_dune/bin
 	mkdir -p $(CURDIR)/_opam/sys_dune/lib