make sure things are really installed after make build-dep

Makefile

@@ -28,16 +28,10 @@ build-dep: build-dep/opam phony
 	@# constraints.  Otherwise, `opam upgrade` may well update some packages to versions
 	@# that are incompatible with our build requirements.
 	@# To achieve this, we create a fake opam package that has our build-dependencies as
-	@# dependencies, but does not actually install anything.
-	@# Reinstalling is needed with opam 1 in case the pin already exists, but the builddep
-	@# package changed.
+	@# dependencies, but does not actually install anything itself.
 	@BUILD_DEP_PACKAGE="$$(egrep "^name:" build-dep/opam | sed 's/^name: *"\(.*\)" */\1/')" && \
 	  echo "# Pinning build-dep package." && \
-	  opam pin add -k path $(OPAMFLAGS) "$$BUILD_DEP_PACKAGE".dev build-dep && \
-	  ((! opam --version | grep "^1\." > /dev/null) || ( \
-	    echo "# Reinstalling build-dep package." && \
-	    opam reinstall $(OPAMFLAGS) "$$BUILD_DEP_PACKAGE" \
-	  ))
+	  opam install $(OPAMFLAGS) build-dep/
 
 # Some files that do *not* need to be forwarded to Makefile.coq
 Makefile: ;