I edited the install rules in debian/, executed ./bootstrap, and dpkg-buildpackage -b -uc -us, which worked without problems. Afterward, I installed the generated Debian packages. The file is located in /usr/lib/codeblocks/plugins/libcon_compiler.so.
When doing strace codeblocks_con --build --target=Debug MyProject.cbp, it shows the following:
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stat("/usr/lib/codeblocks/plugins/libcodecompletion.so", {st_mode=S_IFREG|0644, st_size=1041040, ...}) = 0
stat("/usr/lib/codeblocks/plugins/libcon_compiler.so", {st_mode=S_IFREG|0644, st_size=1018192, ...}) = 0
stat("/home/benjamin/.codeblocks/share/codeblocks/plugins/con_compiler.zip", 0x7fff01890960) = -1 ENOENT (No such file or directory)
stat("/home/benjamin/.codeblocks/share/codeblocks/con_compiler.zip", 0x7fff01890960) = -1 ENOENT (No such file or directory)
stat("/usr/lib/codeblocks/plugins/con_compiler.zip", 0x7fff01890960) = -1 ENOENT (No such file or directory)
stat("/usr/share/codeblocks/con_compiler.zip", 0x7fff01890960) = -1 ENOENT (No such file or directory)
write(2, "Plugin resource not found: libco"..., 46Plugin resource not found: libcon_compiler.zip) = 46
write(2, "\n", 1
) = 1
getdents(3, /* 0 entries */, 32768) = 0
write(1, "Loaded 0 plugins\n", 17Loaded 0 plugins
) = 17
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