Gentoo bug 554258 says:
"While the issue is not immediately noticeable since usually all write operations on those files (e.g. stripping) are done as root. However, this is upstream issue that will eventually cause some random failures.

For example, this will fail if the whole build & install is done as unprivileged user. Or when SELinux (without dac_override) is effective [pointed out by perfinion]."

include/CMakeLists.txt:

FOREACH(f ${HEADERS_GEN_CONFIGURE})

  INSTALL(FILES ${CMAKE_CURRENT_BINARY_DIR}/${f} DESTINATION ${INSTALL_INCLUDEDIR} COMPONENT Development PERMISSIONS OWNER_READ GROUP_READ WORLD_READ)

ENDFOREACH(f)

Should be:

FOREACH(f ${HEADERS_GEN_CONFIGURE})

  INSTALL(FILES ${CMAKE_CURRENT_BINARY_DIR}/${f} DESTINATION ${INSTALL_INCLUDEDIR} COMPONENT Development PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ)

ENDFOREACH(f)