Make Linux updater work with older libc

With this change it requires 2.25 instead of 2.28. This was achieved by
overwriting the results of 2 feature tests (for statx and renameat2),
and patching a file which used statx regardless of the test.

Dockerfile

@@ -38,11 +38,16 @@ RUN make -j`nproc` && make install_sw && rm -rf /build-ssl
 # Build Qt #
 ############
 WORKDIR /build-qt
+# We set the results of the renameat2 and statx feature tests to failure with sed below, but the
+# statx test is actually ignored so this extra patch is needed to disable it.
+COPY disable-statx.patch .
 ENV UPDATER_MODULES=qtbase,qtquickcontrols,qtquickcontrols2,qtsvg,qtgraphicaleffects
 RUN curl -LO https://download.qt.io/archive/qt/5.14/5.14.2/single/qt-everywhere-src-5.14.2.tar.xz && \
     curl -L https://download.qt.io/archive/qt/5.14/5.14.2/single/md5sums.txt | md5sum --check --ignore-missing && \
     tar -xJf qt-everywhere-src-5.14.2.tar.xz && \
     cd qt-everywhere-src-5.14.2 && \
+    sed -i -E 's/tests[.](statx|renameat2)/false/' qtbase/src/corelib/configure.json && \
+    patch qtbase/src/corelib/io/qfilesystemengine_unix.cpp < ../disable-statx.patch && \
     OPENSSL_LIBS='-L/openssl/lib -lssl -lcrypto -lpthread -ldl' ./configure -opensource -confirm-license -release -optimize-size -no-shared -static --c++std=14 -nomake tests -nomake tools -nomake examples -no-gif -no-icu -no-glib -no-qml-debug -opengl desktop -no-eglfs -no-opengles3 -no-angle -no-egl -qt-xcb -xkbcommon -dbus-runtime -qt-freetype -qt-pcre -qt-harfbuzz -qt-libpng -qt-libjpeg -system-zlib -I /openssl/include -openssl-linked -prefix /qt && \
     bash -c "make -j`nproc` module-{$UPDATER_MODULES} && make module-{$UPDATER_MODULES}-install_subtargets" && \
     rm -rf /build-qt
@@ -64,6 +69,11 @@ RUN set -e; for D in . quazip fluid; do cd /updater2/$D && git clean -dXff; done
 WORKDIR /build
 RUN /qt/bin/qmake -config release QMAKE_LFLAGS+="-no-pie" /updater2 && make -j`nproc`
 RUN mv updater2 updater2-nonstripped && strip updater2-nonstripped -o updater2
+# Version check: do not depend on glibc > 2.26
+RUN echo GLIBC_2.26 > target_version && \
+    grep -aoE 'GLIBC_[0-9.]+' updater2 > symbol_versions && \
+    cat target_version symbol_versions | sort -V | tail -1 > max_version && \
+    diff -q target_version max_version
 ARG release
 RUN if [ -n "$release" ]; then cp updater2 UnvanquishedUpdater && 7z -tzip -mx=9 a UnvUpdaterLinux.zip UnvanquishedUpdater; fi
 ENV zipfile=${release:+UnvUpdaterLinux.zip}

disable-statx.patch

@@ -0,0 +1,15 @@
+--- qtbase/src/corelib/io/qfilesystemengine_unix.cpp	2020-03-27 04:49:31.000000000 -0500
++++ qtbase/src/corelib/io/qfilesystemengine_unix.cpp	2021-02-05 14:22:53.044477900 -0600
+@@ -95,12 +95,10 @@
+ #endif
+ #endif
+
+-#if defined(Q_OS_ANDROID)
+ // statx() is disabled on Android because quite a few systems
+ // come with sandboxes that kill applications that make system calls outside a
+ // whitelist and several Android vendors can't be bothered to update the list.
+ #  undef STATX_BASIC_STATS
+-#endif
+
+ #ifndef STATX_ALL
+ struct statx { mode_t stx_mode; };      // dummy