[rocTracer] Protect dependency on roctx64

[junliume]

Introduced by #2391

https://github.com/ROCmSoftwarePlatform/MIOpen/blob/19c6046d1a1d2ac7123fbeaf7775dd7a5749bfd3/src/CMakeLists.txt#L849

Maybe the line is better with

    find_library(LIBTX64 roctx64)
    if(LIBTX64)
        MESSAGE(STATUS "Libtx64: " ${LIBTX64})
        target_internal_library(MIOpen ${LIBTX64})
    endif()

There might be better design when rocTracer is not installed, I think we should protect the case somehow.

Other related issues: the NEEDED below needs to be explicitly set as dependencies for MIOpen package

➜  build git:(develop) ✗ objdump -x lib/libMIOpen.so | grep -A 15 "Dynamic Section"
Dynamic Section:
  RUNPATH              /opt/rocm/lib:/opt/rocm-5.7.0/lib::/opt/rocm/lib
  NEEDED               libamd_comgr.so.2
  NEEDED               librocblas.so.3
  NEEDED               libroctx64.so.4
  NEEDED               libamdhip64.so.5
  NEEDED               libstdc++.so.6
  NEEDED               libm.so.6
  NEEDED               libgcc_s.so.1
  NEEDED               libc.so.6
  NEEDED               ld-linux-x86-64.so.2
  SONAME               libMIOpen.so.1
  RELA                 0x00000000002710c0
  RELASZ               0x00000000006364f8
  RELAENT              0x0000000000000018
  RELACOUNT            0x000000000003c97b

[junliume]

@atamazov @JehandadKhan could you take a look?