ruby: configure mis-detects isnan/isinf on musl

The configure script does not detect isnan/isinf as macros
as is the case in musl:
    checking for isinf... no
    checking for isnan... no

Backport an upstream patch from 2.7.0-preview1 to address this:
    checking whether isinf is declared... yes
    checking whether isnan is declared... yes

(From OE-Core rev: b1afaccdba31341cace4b8d84d118ca76098587e)

Signed-off-by: André Draszik <andre.draszik@jci.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/ruby/ruby/0001-configure.ac-check-finite-isinf-isnan-as-macros-firs.patch

@@ -0,0 +1,101 @@
+From 3a8189530312e81d6c005c396565f985a47f3383 Mon Sep 17 00:00:00 2001
+From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
+Date: Fri, 8 Feb 2019 07:22:55 +0000
+Subject: [PATCH] configure.ac: check finite,isinf,isnan as macros first
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+[ruby-core:91487] [Bug #15595]
+
+git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67036 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
+
+---
+Upstream-Status: Backport [https://github.com/ruby/ruby/commit/74f94b3e6ebf15b76f3b357e754095412b006e94]
+(modified so as to apply cleanly here)
+Signed-off-by: André Draszik <andre.draszik@jci.com>
+---
+ aclocal.m4                    |  1 +
+ configure.ac                  | 13 ++++---------
+ tool/m4/ruby_replace_funcs.m4 | 13 +++++++++++++
+ 3 files changed, 18 insertions(+), 9 deletions(-)
+ create mode 100644 tool/m4/ruby_replace_funcs.m4
+
+diff --git a/aclocal.m4 b/aclocal.m4
+index 18ba297b05..2a907b3467 100644
+--- a/aclocal.m4
++++ b/aclocal.m4
+@@ -13,3 +13,4 @@
+ 
+ m4_ifndef([AC_CONFIG_MACRO_DIRS], [m4_defun([_AM_CONFIG_MACRO_DIRS], [])m4_defun([AC_CONFIG_MACRO_DIRS], [_AM_CONFIG_MACRO_DIRS($@)])])
+ m4_include([acinclude.m4])
++m4_include([tool/m4/ruby_replace_funcs.m4])
+diff --git a/configure.ac b/configure.ac
+index 8a7cee55b8..b97c5b3cc9 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -1189,9 +1189,6 @@ main()
+ 		ac_cv_func_fsync=yes
+ 		ac_cv_func_seekdir=yes
+ 		ac_cv_func_telldir=yes
+-		ac_cv_func_isinf=yes
+-		ac_cv_func_isnan=yes
+-		ac_cv_func_finite=yes
+ 		ac_cv_func_lchown=yes
+ 		ac_cv_func_link=yes
+ 		ac_cv_func_readlink=yes
+@@ -1239,9 +1236,6 @@ main()
+ [netbsd*], [	LIBS="-lm $LIBS"
+ 		],
+ [dragonfly*], [	LIBS="-lm $LIBS"
+-		# isinf() and isnan() are macros on DragonFly.
+-		ac_cv_func_isinf=yes
+-		ac_cv_func_isnan=yes
+ 		],
+ [aix*],[	LIBS="-lm $LIBS"
+ 		ac_cv_func_round=no
+@@ -2213,11 +2207,8 @@ AC_REPLACE_FUNCS(dup2)
+ AC_REPLACE_FUNCS(erf)
+ AC_REPLACE_FUNCS(explicit_bzero)
+ AC_REPLACE_FUNCS(ffs)
+-AC_REPLACE_FUNCS(finite)
+ AC_REPLACE_FUNCS(flock)
+ AC_REPLACE_FUNCS(hypot)
+-AC_REPLACE_FUNCS(isinf)
+-AC_REPLACE_FUNCS(isnan)
+ AC_REPLACE_FUNCS(lgamma_r)
+ AC_REPLACE_FUNCS(memmove)
+ AC_REPLACE_FUNCS(nextafter)
+@@ -2229,6 +2220,10 @@ AC_REPLACE_FUNCS(strlcpy)
+ AC_REPLACE_FUNCS(strstr)
+ AC_REPLACE_FUNCS(tgamma)
+ 
++RUBY_REPLACE_FUNC([finite], [@%:@include <math.h>])
++RUBY_REPLACE_FUNC([isinf], [@%:@include <math.h>])
++RUBY_REPLACE_FUNC([isnan], [@%:@include <math.h>])
++
+ # for missing/setproctitle.c
+ AS_CASE(["$target_os"],
+ [aix* | k*bsd*-gnu | kopensolaris*-gnu | linux* | darwin*], [AC_DEFINE(SPT_TYPE,SPT_REUSEARGV)],
+diff --git a/tool/m4/ruby_replace_funcs.m4 b/tool/m4/ruby_replace_funcs.m4
+new file mode 100644
+index 0000000000..d0612e29a0
+--- /dev/null
++++ b/tool/m4/ruby_replace_funcs.m4
+@@ -0,0 +1,13 @@
++# -*- Autoconf -*-
++dnl RUBY_REPLACE_FUNC [func] [included]
++AC_DEFUN([RUBY_REPLACE_FUNC], [dnl
++    AC_CHECK_DECL([$1],dnl
++        [AC_DEFINE(AS_TR_CPP(HAVE_[$1]))],dnl
++        [AC_REPLACE_FUNCS($1)],dnl
++        [$2])dnl
++])
++
++dnl RUBY_REPLACE_FUNCS [funcs] [included]
++AC_DEFUN([RUBY_REPLACE_FUNCS] [dnl
++    m4_map_args_w([$1], [RUBY_REPLACE_FUNC(], [), [$2]])dnl
++])
+-- 
+2.23.0.rc1
+

meta/recipes-devtools/ruby/ruby_2.5.5.bb

@@ -1,6 +1,7 @@
 require ruby.inc
 
 SRC_URI += " \
+           file://0001-configure.ac-check-finite-isinf-isnan-as-macros-firs.patch \
            file://run-ptest \
            "