ruby: Link with libucontext on musl

coroutines in ruby 2.7+ needs ucontext APIs which are not available in
musl but an external library is available to provide them so use it

Use cached values for ac_cv_func_isnan and ac_cv_func_isinf this is not
detected correctly by configure on musl

on ARM drop using old arm32 implementation of coroutine which is slow and
inefficient

(From OE-Core rev: 406e7a085b0650bdba9f19633dadb7e6ff0149e5)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/ruby/ruby_2.7.0.bb

@@ -1,5 +1,7 @@
 require ruby.inc
 
+DEPENDS_append_libc-musl = " libucontext"
+
 SRC_URI += " \
            file://remove_has_include_macros.patch \
            file://run-ptest \
@@ -25,8 +27,11 @@ EXTRA_OECONF = "\
     --with-pkg-config=pkg-config \
 "
 
-EXTRA_OECONF_append_libc-musl_arm = " --with-coroutine=arm32"
-EXTRA_OECONF_append_libc-musl_armeb = " --with-coroutine=arm32"
+EXTRA_OECONF_append_libc-musl = "\
+    LIBS='-lucontext' \
+    ac_cv_func_isnan=yes \
+    ac_cv_func_isinf=yes \
+"
 
 do_install() {
     oe_runmake 'DESTDIR=${D}' install