tar -zxvf matplotlib-3.1.2.tar.gz
cd matplotlib-3.1.2
python setup.py build

BUILDING MATPLOTLIB
  matplotlib: yes [3.1.2]
      python: yes [3.6.3 (default, Nov 23 2020, 09:56:24)  [GCC 4.8.5 20150623
                  (Red Hat 4.8.5-44)]]
    platform: yes [linux]

OPTIONAL SUBPACKAGES
 sample_data: yes [installing]
       tests: no  [skipping due to configuration]

OPTIONAL BACKEND EXTENSIONS
         agg: yes [installing]
       tkagg: yes [installing; run-time loading from Python Tcl/Tk]
      macosx: no  [Mac OS-X only]

OPTIONAL PACKAGE DATA
        dlls: no  [skipping due to configuration]

/usr/local/python3.6/lib/python3.6/distutils/dist.py:261: UserWarning: Unknown distribution option: 'project_urls'
  warnings.warn(msg)
running build
running build_py
copying lib/matplotlib/mpl-data/matplotlibrc -> build/lib.linux-aarch64-3.6/matplotlib/mpl-data
UPDATING build/lib.linux-aarch64-3.6/matplotlib/_version.py
set build/lib.linux-aarch64-3.6/matplotlib/_version.py to '3.1.2'
running build_ext
building 'matplotlib._png' extension
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -DPY_ARRAY_UNIQUE_SYMBOL=MPL_matplotlib__png_ARRAY_API -DNPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION -D__STDC_FORMAT_MACROS=1 -I/home/wah/venv/lib/python3.6/site-packages/numpy/core/include -I/home/wah/venv/include -I/usr/local/python3.6/include/python3.6m -c src/checkdep_libpng.c -o build/temp.linux-aarch64-3.6/src/checkdep_libpng.o -I/usr/include/libpng15
src/checkdep_libpng.c:2:9: note: #pragma message: Compiling with libpng version 1.5.13.
 #pragma message("Compiling with libpng version " PNG_LIBPNG_VER_STRING ".")
         ^
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -DPY_ARRAY_UNIQUE_SYMBOL=MPL_matplotlib__png_ARRAY_API -DNPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION -D__STDC_FORMAT_MACROS=1 -I/home/wah/venv/lib/python3.6/site-packages/numpy/core/include -I/home/wah/venv/include -I/usr/local/python3.6/include/python3.6m -c src/_png.cpp -o build/temp.linux-aarch64-3.6/src/_png.o -I/usr/include/libpng15
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -DPY_ARRAY_UNIQUE_SYMBOL=MPL_matplotlib__png_ARRAY_API -DNPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION -D__STDC_FORMAT_MACROS=1 -I/home/wah/venv/lib/python3.6/site-packages/numpy/core/include -I/home/wah/venv/include -I/usr/local/python3.6/include/python3.6m -c src/mplutils.cpp -o build/temp.linux-aarch64-3.6/src/mplutils.o -I/usr/include/libpng15
g++ -pthread -shared build/temp.linux-aarch64-3.6/src/checkdep_libpng.o build/temp.linux-aarch64-3.6/src/_png.o build/temp.linux-aarch64-3.6/src/mplutils.o -L/usr/local/python3.6/lib -lpython3.6m -o build/lib.linux-aarch64-3.6/matplotlib/_png.cpython-36m-aarch64-linux-gnu.so -lpng15
collect2: error: ld terminated with signal 9 [Killed]
error: command 'g++' failed with exit status 1