$ CC=gcc-10 CXX=g++-10 make all
(redacted)
[*] Testing the CC wrapper and instrumentation output...
unset AFL_USE_ASAN AFL_USE_MSAN; ASAN_OPTIONS=detect_leaks=0 AFL_QUIET=1 AFL_INST_RATIO=100 AFL_PATH=. AFL_CC=gcc-10 ./afl-gcc-fast -O3 -g -funroll-loops -D_FORTIFY_SOURCE=2 -Wall -Iinclude -Wno-pointer-sign -DAFL_PATH=\"/usr/local/lib/afl\" -DBIN_PATH=\"/usr/local/bin\" -DGCC_VERSION=\"\" -DGCC_BINDIR=\"\" -Wno-unused-function  ./test-instr.c -o test-instr -lrt

[-] PROGRAM ABORT : GCC and plugin have incompatible versions, expected GCC 10.3.0, is 10.3.0
         Location : plugin_init(), instrumentation/afl-gcc-pass.so.cc:927

make[1]: *** [GNUmakefile.gcc_plugin:154: test_build] Error 1
make[1]: Leaving directory 'AFLplusplus-4.01c'
make: [GNUmakefile:321: gcc_plugin] Error 2 (ignored)
[*] Testing the CC wrapper afl-cc and its instrumentation output...
afl-cc++4.01c by Michal Zalewski, Laszlo Szekeres, Marc Heuse - mode: GCC_PLUGIN-DEFAULT

[-] PROGRAM ABORT : GCC and plugin have incompatible versions, expected GCC 10.3.0, is 9.4.0
         Location : plugin_init(), instrumentation/afl-gcc-pass.so.cc:927

Oops, afl-cc failed
make: *** [GNUmakefile:534: test_build] Error 1