Do not remove RPM build root

Removing the buildroot contents in %install has not been necessary or
permitted for a long time. See
https://docs.fedoraproject.org/en-US/packaging-guidelines/#_tags_and_sections

perl-Encode-Detect.spec

@@ -38,7 +38,6 @@ EOF
 ./Build test
 
 %install
-%{__rm} -rf "${RPM_BUILD_ROOT}"
 ./Build install destdir="${RPM_BUILD_ROOT}" create_packlist=0
 find "${RPM_BUILD_ROOT}" -type f -name "*.bs" -size 0 -exec %{__rm} -f {} \;
 find "${RPM_BUILD_ROOT}" -depth -type d -exec rmdir {} 2>/dev/null \;