occt 7.2/7.4 build error: cannot find -lXmu about oce

[roipoussiere]

After redirecting stderr to a file, I found the error message (which was hidden by some really verbose unfinished jobs):

/usr/lib/gcc/x86_64-unknown-linux-gnu/9.2.0/../../../../x86_64-unknown-linux-gnu/bin/ld: cannot find -lXmu
collect2: error: ld returned 1 exit status
make[2]: *** [src/TKService/CMakeFiles/TKService.dir/build.make:440: lin64/gcc/lib/libTKService.so.7.2.0] Error 1
make[1]: *** [CMakeFiles/Makefile2:1190: src/TKService/CMakeFiles/TKService.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

This error appears on both occt 7.2 and 7.4

[roipoussiere]

As suggested here I ran ld -lXmu --verbose:

[...]
ld: mode elf_x86_64
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libXmu.so failed
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libXmu.a failed
attempt to open /usr/lib/x86_64-linux-gnu/libXmu.so failed
attempt to open /usr/lib/x86_64-linux-gnu/libXmu.a failed
attempt to open /usr/lib/libXmu.so failed
attempt to open /usr/lib/libXmu.a failed
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libXmu.so failed
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libXmu.a failed
ld: cannot find -lXmu

So libxmu was missing, installing it fixed the problem.