QGIS » QGIS Application

On branch QGIS 3.4.3 (release-3.4), freshly pulled from the git repo, here is the "cmake-gui" output after "configure" and "generate":

QGIS version: 3.4.3 Madeira (30403)
Found OpenCL C++ headers: /usr/include
Could not find GRASS 7
Found Proj: /usr/local/lib/libproj.so (6.0.0)
Found GEOS: /usr/lib/x86_64-linux-gnu/libgeos_c.so (3.6.2)
Found GDAL: /usr/local/lib/libgdal.so (2.4.0dev-283265213f-dirty)
Found Expat: /usr/lib/x86_64-linux-gnu/libexpat.so
Found Spatialindex: /usr/lib/x86_64-linux-gnu/libspatialindex.so
Found Qwt: /usr/lib/libqwt-qt5.so (6.1.3)
Found libzip: /usr/lib/x86_64-linux-gnu/libzip.so
Found Sqlite3: /usr/lib/x86_64-linux-gnu/libsqlite3.so
Found PostgreSQL: /usr/lib/x86_64-linux-gnu/libpq.so
Qt WebKit support enabled
Found Qt version: 5.9.5
Found QScintilla2: /usr/lib/libqscintilla2_qt5.so (2.10.2)
Found QtKeychain: /usr/lib/x86_64-linux-gnu/libqt5keychain.so
Found QCA: /usr/lib/x86_64-linux-gnu/libqca-qt5.so (2.1.3)
Found QCA OpenSSL plugin
Pedantic compiler settings enabled
Found Python executable: /usr/bin/python3
Found Python version: 3.6.7
Found Python library: /usr/lib/x86_64-linux-gnu/libpython3.6m.so
Found Python site-packages: /usr/lib/python3/dist-packages
Found PyQt5 version: 5.10.1
Found SIP version: 4.19.7
Found QScintilla2 PyQt module: 2.10.2
txt2tags not found - disabled
HDF5: Using hdf5 compiler wrapper to determine C configuration
Found GSL: -L/usr/lib/x86_64-linux-gnu -lgsl -lgslcblas -lm
Qsci sip file not found - disabling bindings for derived classes
Ctest Binary Directory set to: /opt/QGIS/build_34/output/bin
Configuring done
Generating done

1. I wonder why it cannot find "Qsci sip file"? What is this file? Which package it is bundled with?

Then, "make" is issuing this error:
[ 79%] Generating core/sip_corepart0.cpp, core/sip_corepart1.cpp, core/sip_corepart2.cpp, core/sip_corepart3.cpp

sip: Unable to find file "QtXml/QtXmlmod.sip"
python/CMakeFiles/python_module_qgis__core.dir/build.make:523: recipe for target 'python/core/sip_corepart0.cpp' failed
make²: * [python/core/sip_corepart0.cpp] Error 1
make²: Deleting file 'python/core/sip_corepart0.cpp'
CMakeFiles/Makefile2:3958: recipe for target 'python/CMakeFiles/python_module_qgis__core.dir/all' failed
make¹: [python/CMakeFiles/python_module_qgis__core.dir/all] Error 2
Makefile:162: recipe for target 'all' failed
make: * [all] Error 2

2. How to fix it, if possible?

My OS is Ubuntu 18.04: 4.15.0-43-generic x86_64 GNU/Linux