Disable btrfs in RHEL builds

btrfs-progs is not supported on RHEL.  BUILDTAGS is already set properly
to compile if not present.

podman.spec

@@ -7,6 +7,12 @@
 %global debug_package %{nil}
 %endif
 
+%if 0%{?rhel}
+%bcond_with btrfs
+%else
+%bcond_without btrfs
+%endif
+
 %global provider github
 %global provider_tld com
 %global project containers
@@ -48,7 +54,9 @@ Source2: %{git_gvproxy}/archive/%{commit_gvproxy}/%{repo_gvproxy}-%{commit_gvpro
 Provides: %{name}-manpages = %{epoch}:%{version}-%{release}
 BuildRequires: gettext-envsubst
 BuildRequires: go-md2man
+%if %{with btrfs}
 BuildRequires: btrfs-progs-devel
+%endif
 BuildRequires: gcc
 BuildRequires: glib2-devel
 BuildRequires: glibc-devel