/usr/lib/x86_64-linux-gnu/libQtGui.prl is in libqt4-dev 4:4.8.7+dfsg-7ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | QMAKE_PRO_INPUT = gui.pro
QMAKE_PRL_TARGET = libQtGui.so.4.8.7
QMAKE_PRL_DEFINES = QT_SHARED
QMAKE_PRL_CONFIG = lex yacc warn_on uic resources qt warn_on release incremental link_prl gdb_dwarf_index shared def_files_disabled exceptions no_mocdepend release stl qt_no_framework system-sqlite release largefile stl precompile_header mmx 3dnow sse sse2 sse3 ssse3 sse4_1 sse4_2 avx dylib create_prl link_prl depend_includepath QTDIR_build nostrip x11 qt_install_headers qt warn_on depend_includepath qmake_cache target_qt hide_symbols bsymbolic_functions create_pc create_libtool explicitlib x11sm opentype moc thread x11lib x11inc dll shared
QMAKE_PRL_VERSION = 4.8.7
QMAKE_PRL_LIBS =
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