Disable pthread on RISC-V (riscv64)

Until we can understand the build failure related to pthread thread
model it's better we disable it:

BUILDSTDERR: rb_mjiminiruby: thread_pthread.c:1995: rb_sigwait_fd_put: Assertion `old == th' failed.
BUILDSTDERR: make: *** [uncommon.mk:233: .ext/include/riscv64-linux/rb_mjit_min_header-2.6.3.h] Aborted (core dumped)

Signed-off-by: David Abdurachmanov <david.abdurachmanov@sifive.com>

riscv-disable-pthread.patch

@@ -0,0 +1,14 @@
+diff --git a/configure.ac b/configure.ac
+index 363afee..3276ade 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -770,6 +770,9 @@ AS_CASE(["$target_os"],
+   enable_pthread=yes
+   ])
+ 
++# Disable pthread on RISC-V until compile assert is sorted out
++AS_CASE(["$target_cpu"],[riscv*],[enable_pthread=no],[])
++
+ dnl Checks for libraries.
+ AS_CASE(["$target_os"],[*bsd*|dragonfly*],[],[ac_cv_func_daemon=no])
+ 

ruby.spec

@@ -22,7 +22,7 @@
 
 
 %global release 121
-%{!?release_string:%global release_string %{?development_release:0.}%{release}%{?development_release:.%{development_release}}%{?dist}}
+%{!?release_string:%global release_string %{?development_release:0.}%{release}%{?development_release:.%{development_release}}.0.riscv64%{?dist}}
 
 # The RubyGems library has to stay out of Ruby directory tree, since the
 # RubyGems should be share by all Ruby implementations.
@@ -154,6 +154,9 @@ Patch22: ruby-2.6.0-config-support-include-directive.patch
 # https://github.com/ruby/openssl/pull/217
 Patch23: ruby-2.6.0-use-larger-keys-for-SSL-tests.patch
 
+# Disable pthread on Linux RISC-V (riscv64)
+Patch30: riscv-disable-pthread.patch
+
 Requires: %{name}-libs%{?_isa} = %{version}-%{release}
 Suggests: rubypick
 Recommends: ruby(rubygems) >= %{rubygems_version}
@@ -547,6 +550,10 @@ rm -rf ext/fiddle/libffi*
 %patch22 -p1
 %patch23 -p1
 
+%ifarch riscv64
+%patch30 -p1
+%endif
+
 # Provide an example of usage of the tapset:
 cp -a %{SOURCE3} .
 
@@ -1182,6 +1189,9 @@ make check TESTS="-v $DISABLE_TESTS" MSPECOPT="-fs $MSPECOPTS"
 %{_mandir}/man5/gemfile.5*
 
 %changelog
+* Tue Jul 23 2019 David Abdurachmanov <david.abdurachmanov@sifive.com> - 2.6.3-121.0.riscv64
+- Disable pthread on RISC-V (riscv64)
+
 * Tue Jun 25 2019 Vít Ondruch <vondruch@redhat.com> - 2.6.3-121
 - Properly support %%prerelease in %%gemspec_ macros.