These are the packages that would be merged, in order:

Calculating dependencies  . ... done!
[ebuild     U ~] dev-ruby/rubygems-2.7.6::gentoo [2.6.14::gentoo] USE="-server {-test}" RUBY_TARGETS="ruby24 -ruby22 -ruby23 -ruby25%" 0 KiB

Total: 1 package (1 upgrade), Size of downloads: 0 KiB

Would you like to merge these packages? [Yes/No] >>> Verifying ebuild manifests
>>> Jobs: 0 of 1 complete, 1 running                Load avg: 1.45, 1.57, 1.95
>>> Emerging (1 of 1) dev-ruby/rubygems-2.7.6::gentoo
>>> Jobs: 0 of 1 complete, 1 running                Load avg: 1.45, 1.57, 1.95
>>> Failed to emerge dev-ruby/rubygems-2.7.6, Log file:
>>> Jobs: 0 of 1 complete, 1 running                Load avg: 1.45, 1.57, 1.95
>>>  '/var/tmp/portage/dev-ruby/rubygems-2.7.6/temp/build.log'
>>> Jobs: 0 of 1 complete, 1 running                Load avg: 1.45, 1.57, 1.95
>>> Jobs: 0 of 1 complete, 1 running, 1 failed      Load avg: 1.45, 1.57, 1.95
>>> Jobs: 0 of 1 complete, 1 failed                 Load avg: 1.45, 1.57, 1.95

 * Package:    dev-ruby/rubygems-2.7.6
 * Repository: gentoo
 * Maintainer: ruby@gentoo.org
 * USE:        abi_x86_64 amd64 elibc_glibc kernel_linux ruby_targets_ruby24 userland_GNU
 * FEATURES:   preserve-libs sandbox userpriv usersandbox
>>> Unpacking source...
>>> Unpacking rubygems-2.7.6.tgz to /var/tmp/portage/dev-ruby/rubygems-2.7.6/work/all
>>> Source unpacked in /var/tmp/portage/dev-ruby/rubygems-2.7.6/work
>>> Preparing source in /var/tmp/portage/dev-ruby/rubygems-2.7.6/work ...
 * Running prepare phase for all ...
 * Running prepare phase for all ...
 * Adjusting to prefix /
 *   operating_system.rb ...
 [ ok ]
 * Running source copy phase for ruby24 ...
cp: cannot create hard link 'ruby24/rubygems-2.7.6/test/rubygems/test_gem_installer.rb' to 'all/rubygems-2.7.6/test/rubygems/test_gem_installer.rb': File exists
 * ERROR: dev-ruby/rubygems-2.7.6::gentoo failed (prepare phase):
 *   Unable to copy ruby24 environment
 * 
 * Call stack:
 *     ebuild.sh, line  124:  Called src_prepare
 *   environment, line 4254:  Called ruby-ng_src_prepare
 *   environment, line 4073:  Called _ruby_each_implementation '_ruby_source_copy'
 *   environment, line  404:  Called _ruby_invoke_environment 'ruby24' '_ruby_source_copy'
 *   environment, line  529:  Called _ruby_source_copy
 *   environment, line  535:  Called die
 * The specific snippet of code:
 *       cp -prlP all ${_ruby_implementation} || die "Unable to copy ${_ruby_implementation} environment"
 * 
 * If you need support, post the output of `emerge --info '=dev-ruby/rubygems-2.7.6::gentoo'`,
 * the complete build log and the output of `emerge -pqv '=dev-ruby/rubygems-2.7.6::gentoo'`.
!!! When you file a bug report, please include the following information:
GENTOO_VM=  CLASSPATH="" JAVA_HOME=""
JAVACFLAGS="" COMPILER=""
and of course, the output of emerge --info =rubygems-2.7.6
 * The complete build log is located at '/var/tmp/portage/dev-ruby/rubygems-2.7.6/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/dev-ruby/rubygems-2.7.6/temp/environment'.
 * Working directory: '/var/tmp/portage/dev-ruby/rubygems-2.7.6/work'
 * S: '/var/tmp/portage/dev-ruby/rubygems-2.7.6/work/ruby24/rubygems-2.7.6'