elfdeps: look for 64 bit library matches first if binary is 64 bit

[nevun]

If you had 32 bits libraries in /lib, landrun --ldd would pick those before the 64 bit library in /lib64.

This MR just changes the lookup order if the binary we are running is 64 bit.

before:

$ ./landrun --log-level debug  --ldd --add-exec /bin/nc
[landrun:debug] 2025/12/03 11:33:45 Added executable path: /bin/nc
[landrun:debug] 2025/12/03 11:33:45 Added library paths: [/etc/ld.so.cache /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/libnl-3.so.200 /lib/libm.so.6 /lib/libc.so.6 /lib64/libcrypto.so.3 /lib/ld-linux.so.2 /lib/libz.so.1 /lib64/libnl-route-3.so.200 /lib/libgcc_s.so.1]
[landrun] 2025/12/03 11:33:45 Sandbox config: {ReadOnlyPaths:[] ReadWritePaths:[] ReadOnlyExecutablePaths:[/bin/nc /etc/ld.so.cache /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/libnl-3.so.200 /lib/libm.so.6 /lib/libc.so.6 /lib64/libcrypto.so.3 /lib/ld-linux.so.2 /lib/libz.so.1 /lib64/libnl-route-3.so.200 /lib/libgcc_s.so.1] ReadWriteExecutablePaths:[] BindTCPPorts:[] ConnectTCPPorts:[] BestEffort:false UnrestrictedFilesystem:false UnrestrictedNetwork:false}
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /bin/nc
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /etc/ld.so.cache
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/ld-linux-x86-64.so.2
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libssl.so.3
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libpcap.so.1
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libibverbs.so.1
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libnl-3.so.200
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libm.so.6
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libc.so.6
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libcrypto.so.3
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/ld-linux.so.2
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libz.so.1
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib64/libnl-route-3.so.200
[landrun:debug] 2025/12/03 11:33:45 Adding read-only executable path: /lib/libgcc_s.so.1
[landrun:debug] 2025/12/03 11:33:45 Applying Landlock restrictions
[landrun] 2025/12/03 11:33:45 Landlock restrictions applied successfully
[landrun] 2025/12/03 11:33:45 Executing: [/bin/nc]
/bin/nc: error while loading shared libraries: libm.so.6: cannot open shared object file: Permission denied

Notice it resolves four deps to their 32 bit version in /lib

After this MR:

$ ./landrun --log-level debug  --ldd --add-exec /bin/nc
[landrun:debug] 2025/12/03 12:04:28 Added executable path: /bin/nc
[landrun:debug] 2025/12/03 12:04:28 Added library paths: [/etc/ld.so.cache /lib64/libm.so.6 /lib64/libc.so.6 /lib64/libcrypto.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libz.so.1 /lib64/libnl-route-3.so.200 /lib64/libnl-3.so.200 /lib64/libgcc_s.so.1]
[landrun] 2025/12/03 12:04:28 Sandbox config: {ReadOnlyPaths:[] ReadWritePaths:[] ReadOnlyExecutablePaths:[/bin/nc /etc/ld.so.cache /lib64/libm.so.6 /lib64/libc.so.6 /lib64/libcrypto.so.3 /lib64/libpcap.so.1 /lib64/libibverbs.so.1 /lib64/ld-linux-x86-64.so.2 /lib64/libssl.so.3 /lib64/libz.so.1 /lib64/libnl-route-3.so.200 /lib64/libnl-3.so.200 /lib64/libgcc_s.so.1] ReadWriteExecutablePaths:[] BindTCPPorts:[] ConnectTCPPorts:[] BestEffort:false UnrestrictedFilesystem:false UnrestrictedNetwork:false}
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /bin/nc
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /etc/ld.so.cache
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libm.so.6
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libc.so.6
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libcrypto.so.3
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libpcap.so.1
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libibverbs.so.1
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/ld-linux-x86-64.so.2
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libssl.so.3
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libz.so.1
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libnl-route-3.so.200
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libnl-3.so.200
[landrun:debug] 2025/12/03 12:04:28 Adding read-only executable path: /lib64/libgcc_s.so.1
[landrun:debug] 2025/12/03 12:04:28 Applying Landlock restrictions
[landrun] 2025/12/03 12:04:28 Landlock restrictions applied successfully
[landrun] 2025/12/03 12:04:28 Executing: [/bin/nc]
Ncat: You must specify a host to connect to. QUITTING.

Now it works