enable system libyaml with patch

ghc-yaml.spec

@@ -12,7 +12,7 @@
 Name:           ghc-%{pkg_name}
 Version:        0.11.1.0
 # can only be reset when all subpkgs bumped
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        Support for parsing and rendering YAML documents
 
 License:        BSD
@@ -21,6 +21,7 @@ Url:            https://hackage.haskell.org/package/%{pkg_name}
 Source0:        https://hackage.haskell.org/package/%{pkgver}/%{pkgver}.tar.gz
 Source1:        https://hackage.haskell.org/package/%{libyaml}/%{libyaml}.tar.gz
 # End cabal-rpm sources
+Patch1:         system-libyaml.patch
 
 # Begin cabal-rpm deps:
 BuildRequires:  ghc-Cabal-devel
@@ -98,7 +99,7 @@ This package provides the Haskell %{pkg_name} profiling library.
 %global main_version %{version}
 
 %if %{defined ghclibdir}
-%ghc_lib_subpackage %{libyaml}
+%ghc_lib_subpackage -c libyaml-devel%{?_isa} %{libyaml}
 %endif
 
 %global version %{main_version}
@@ -108,9 +109,9 @@ This package provides the Haskell %{pkg_name} profiling library.
 # Begin cabal-rpm setup:
 %setup -q -n %{pkgver} -a1
 # End cabal-rpm setup
+%patch1 -p1 -b .orig
 (
 cd %{libyaml}
-cabal-tweak-flag system-libyaml True
 # remove the bundled lib
 rm -r libyaml_src
 )
@@ -156,6 +157,9 @@ rm -r libyaml_src
 
 
 %changelog
+* Thu Aug  8 2019 Jens Petersen <petersen@redhat.com> - 0.11.1.0-2
+- patch .cabal for system libyaml
+
 * Thu Jul 25 2019 Jens Petersen <petersen@redhat.com> - 0.11.1.0-1
 - update to 0.11.1.0
 - subpackage libyaml

system-libyaml.patch

@@ -0,0 +1,13 @@
+--- yaml-0.11.1.0/libyaml-0.1.1.0/libyaml.cabal~	2019-02-12 09:55:57.000000000 +0100
++++ yaml-0.11.1.0/libyaml-0.1.1.0/libyaml.cabal 	2019-08-08 22:15:56.350202056 +0200
+@@ -38,8 +38,8 @@
+ 
+ flag system-libyaml
+   description: Use the system-wide libyaml instead of the bundled copy
+-  manual: False
+-  default: False
++  manual: True
++  default: True
+ 
+ library
+   exposed-modules: