The exec_prefix seems to be correct now.

ruby-2.0.0-revert-unexpand-exec-prefix.patch

@@ -1,43 +0,0 @@
-* Unmerged path ChangeLog
-diff --git a/configure.in b/configure.in
-index be7d4fe..2d511e5 100644
---- a/configure.in
-+++ b/configure.in
-@@ -2574,14 +2574,9 @@ AS_CASE(["$target_os"],
- 
- AC_SUBST(setup)
- 
--test x"$prefix" = xNONE && prefix=$ac_default_prefix
--test x"${exec_prefix}" = xNONE && exec_prefix="$prefix"
--pat=`echo "${exec_prefix}" | tr -c '\012' .`'\(.*\)'
--for var in bindir libdir; do
--    eval val='"$'$var'"'
--    AS_CASE(["$val"], ["${exec_prefix}"*], [val='${exec_prefix}'"`expr \"$val\" : \"$pat\"`"])
--    eval $var='"$val"'
--done
-+if test "$prefix" = NONE; then
-+  prefix=$ac_default_prefix
-+fi
- 
- BTESTRUBY='$(MINIRUBY)'
- if test x"$cross_compiling" = xyes; then
-@@ -3211,9 +3216,6 @@ AS_CASE(["$target_os"],
- 
- shvar_to_cpp() {
-     var="$1" val="$2"
--    exec_prefix_pat="`echo \"${exec_prefix}\" | sed 's/\\./\\\\./g'`"
--    arch_pat="`echo \"${arch}\" | sed 's/\\./\\\\./g'`"
--    sitearch_pat="`echo \"${sitearch}\" | sed 's/\\./\\\\./g'`"
-     val="`echo '\"'\"${val}\"'\"' |
- 	sed \
- 	    -e 's/\${\([[A-Z][A-Z_]]*\)}/\"\1\"/g' \
-@@ -3236,9 +3238,6 @@ shvar_to_cpp() {
- 	    -e 's/\${rubyarchprefix}/\"RUBY_ARCH_PREFIX_FOR(arch)\"/g' \
- 	    -e 's/\${rubysitearchprefix}/\"RUBY_SITEARCH_PREFIX_FOR(arch)\"/g' \
- 	    -e 's/\${exec_prefix}/\"RUBY_EXEC_PREFIX\"/g' \
--	    -e \"s|${exec_prefix_pat}/|\"'\"RUBY_EXEC_PREFIX\"/|g' \
--	    -e \"s|${arch_pat}|\"'\"arch\"|g' \
--	    -e \"s|${sitearch_pat}|\"'\"sitearch\"|g' \
- 	    -e 's|^\\\"NONE/|RUBY_EXEC_PREFIX\\\"/|' \
- 	    -e 's|^\\\"NONE\\\"|\\\"'\"${prefix}\"'\\\"|' \
- 	    -e 's/^\\\"\\\"\(.\)/\1/;s/\(.\)\\\"\\\"$/\1/'

ruby.spec

@@ -135,10 +135,6 @@ Patch13: rubygems-2.0.0-Do-not-modify-global-Specification.dirs-during-insta.pat
 # This prevents issues, when ruby configuration specifies --with-ruby-version=''.
 # https://github.com/rubygems/rubygems/pull/455
 Patch14: rubygems-2.0.0-Fixes-for-empty-ruby-version.patch
-# Fixes issues with wrong value of Rubygem's shebang introduced in r39267.
-# https://bugs.ruby-lang.org/issues/7915
-# TODO:
-Patch15: ruby-2.0.0-revert-unexpand-exec-prefix.patch
 
 Requires: %{name}-libs%{?_isa} = %{version}-%{release}
 Requires: ruby(rubygems) >= %{rubygems_version}
@@ -402,7 +398,6 @@ Tcl/Tk interface for the object-oriented scripting language Ruby.
 %patch12 -p1
 %patch13 -p1
 %patch14 -p1
-%patch15 -p1
 
 # Provide an example of usage of the tapset:
 cp -a %{SOURCE3} .