R: fix build on aarch64 by removing a failing test

I believe this test is currently incorrect on aarch64 and expects a
warning about loss of precision with much smaller numbers than the
platform's long doubles can handle.

pkgs/applications/science/math/R/0001-Disable-test-pending-upstream-fix.patch

@@ -0,0 +1,26 @@
+From 85ede2cf452800710de136f4f864921d3bb9773c Mon Sep 17 00:00:00 2001
+From: Tom Hall <tahall256@protonmail.ch>
+Date: Fri, 21 Feb 2020 22:56:06 +0000
+Subject: [PATCH] Disable test pending upstream fix
+
+See https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17718
+---
+ tests/reg-tests-1d.R | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/tests/reg-tests-1d.R b/tests/reg-tests-1d.R
+index 9b551a1fc8..18ce6027ed 100644
+--- a/tests/reg-tests-1d.R
++++ b/tests/reg-tests-1d.R
+@@ -3079,7 +3079,7 @@ stopifnot(exprs = {
+     x[1:52] %% 3 == 2:1
+    -x[1:52] %% 3 == 1:2
+ }) # larger x suffer from cancellation (well, warning too early now):
+-tools::assertWarning(x[60:68] %% 3)
++#tools::assertWarning(x[60:68] %% 3)
+ 
+ 
+ ## Hilmar Berger's on R-devel list: 'data.frame() == NULL' etc
+-- 
+2.24.1
+

pkgs/applications/science/math/R/default.nix

@@ -27,6 +27,10 @@ stdenv.mkDerivation rec {
 
   patches = [
     ./no-usr-local-search-paths.patch
+  ] ++ stdenv.lib.optionals stdenv.hostPlatform.isAarch64 [
+    # Remove a test which fails on aarch64.
+    # See https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17718
+    ./0001-Disable-test-pending-upstream-fix.patch
   ];
 
   prePatch = stdenv.lib.optionalString stdenv.isDarwin ''