Disable bootstrapping by default.

Use the previously built (in Fedora) OCaml compiler to build the new
compiler.

Provide --with bootstrap if people want to build OCaml using the
embedded binary compiler shipped with upstream sources.

ocaml.spec

@@ -25,9 +25,15 @@
 # Architectures where parallel builds fail.
 #%global no_parallel_build_arches aarch64
 
+# If you want to bootstrap OCaml on a brand new architecture, or if
+# you want to build OCaml without requiring an existing OCaml package,
+# or if you want to build OCaml exactly as it is built upstream (using
+# a binary ocamlc from the previous build), then use ‘--with bootstrap’.
+%bcond_with bootstrap
+
 Name:           ocaml
 Version:        4.07.0
-Release:        2%{?dist}
+Release:        3%{?dist}
 
 Summary:        OCaml compiler and programming environment
 
@@ -69,6 +75,10 @@ Patch0007:      0007-Adapt-to-4.07.patch
 # Sent upstream 2018-06-05.
 Patch0008:      0008-riscv-Emit-debug-info.patch
 
+%if ! %{with bootstrap}
+BuildRequires:  ocaml
+%endif
+
 BuildRequires:  gcc
 BuildRequires:  binutils-devel
 BuildRequires:  ncurses-devel
@@ -194,7 +204,10 @@ may not be portable between versions.
 %prep
 %setup -q -T -b 0 -n %{name}-%{version}
 %autopatch -p1
-
+%if ! %{with bootstrap}
+cp %{_bindir}/ocamlc.byte boot/ocamlc
+cp %{_bindir}/ocamllex.byte boot/ocamllex
+%endif
 
 %build
 %ifnarch %{no_parallel_build_arches}
@@ -425,6 +438,9 @@ find $RPM_BUILD_ROOT \( -name '*.cmt' -o -name '*.cmti' \) -a -delete
 
 
 %changelog
+* Fri Aug 17 2018 Richard W.M. Jones <rjones@redhat.com> - 4.07.0-3
+- Bootstrap from previously build Fedora compiler by default.
+
 * Fri Jul 13 2018 Fedora Release Engineering <releng@fedoraproject.org> - 4.07.0-2
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_29_Mass_Rebuild