net-misc/unison: fix parallel build bug.

Reference: bcpierce00/unison#100
Credit: Robert Forsman, Coacher, José María Fernández González
Credit: Frank Steinmetzger, WGH
Closes: https://bugs.gentoo.org/582666

Package-Manager: Portage-2.3.3, Repoman-2.3.1

net-misc/unison/files/unison-2.48.4-Makefile-dep.patch

@@ -0,0 +1,20 @@
+Makefile.OCaml: fswatch.cmi depends on ubase/prefs.cmi.
+
+  The dependency is needed to compile unison
+  in parallel.
+
+Reference: https://github.com/bcpierce00/unison/pull/100
+
+diff --git a/Makefile.OCaml b/Makefile.OCaml
+index 21610ce..84fe7ad 100644
+--- a/Makefile.OCaml
++++ b/Makefile.OCaml
+@@ -426,6 +426,8 @@ win32rc/unison.res.lib: win32rc/unison.res
+ 	@echo "$(CAMLC): $< ---> $@"
+ 	$(CAMLC) $(CAMLFLAGS) -c $(CWD)/$<
+
++fswatch.cmi : ubase/prefs.cmi
++
+ %.cmo: %.ml
+ 	@echo "$(OCAMLC): $< ---> $@"
+ 	$(OCAMLC) $(CAMLFLAGS) -c $(CWD)/$<

net-misc/unison/unison-2.48.4.ebuild

@@ -30,6 +30,11 @@ SRC_URI="https://www.seas.upenn.edu/~bcpierce/unison/download/releases/${P}/${P}
 		https://www.seas.upenn.edu/~bcpierce/unison/download/releases/${P}/${P}-manual.html )"
 S="${WORKDIR}"/src
 
+src_prepare() {
+	epatch "${FILESDIR}"/${PN}-2.48.4-Makefile-dep.patch
+	default
+}
+
 src_compile() {
 	local myconf