Add libarchive decompression backend

compressed_archive/libarchive/libarchive-wrapper.pri

@@ -0,0 +1,22 @@
+INCLUDEPATH += $$PWD
+DEPENDPATH += $$PWD
+
+HEADERS += $$PWD/extract_delegate.h \
+           $$PWD/compressed_archive.h
+
+SOURCES += $$PWD/compressed_archive.cpp
+
+if(mingw|unix):!contains(QT_CONFIG, no-pkg-config):packagesExist(libarchive) {
+  message(Using system provided libarchive installation found by pkg-config.)
+  CONFIG += link_pkgconfig
+  PKGCONFIG += libarchive
+  DEFINES += use_libarchive
+  }
+else:unix:exists(/usr/include/archive.h) {
+  message(Using system provided libarchive installation.)
+  LIBS += -larchive
+  DEFINES += use_libarchive
+}
+else {
+  error(Missing dependency: libarchive decompression backend. Please install libarchive on your system)
+}