ROCtracer: Include as System library

Because of GNU extensions in the roctracer include files for the legacy include.
But we should make this `-isystem` anyway to be robust for the future.

The 5.2 deprecated include file `<roctracer_ext.h>` throws warnings
because they rely on GNU extensions:
```
In file included from /opt/rocm/hip/../roctracer/include/ext/prof_protocol.h:27:
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:70:7: warning: anonymous structs are a GNU extension [-Wgnu-anonymous-struct]
      struct {
      ^
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:70:7: warning: anonymous types declared in an anonymous union are an extension [-Wnested-anon-types]
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:75:7: warning: anonymous types declared in an anonymous union are an extension [-Wnested-anon-types]
      struct {
      ^
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:82:7: warning: anonymous structs are a GNU extension [-Wgnu-anonymous-struct]
      struct {
      ^
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:86:7: warning: anonymous structs are a GNU extension [-Wgnu-anonymous-struct]
      struct {
      ^
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:90:7: warning: anonymous structs are a GNU extension [-Wgnu-anonymous-struct]
      struct {
      ^
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:82:7: warning: anonymous types declared in an anonymous union are an extension [-Wnested-anon-types]
      struct {
      ^
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:86:7: warning: anonymous types declared in an anonymous union are an extension [-Wnested-anon-types]
      struct {
      ^
/opt/rocm/hip/../roctracer/include/ext/../../../include/roctracer/ext/prof_protocol.h:90:7: warning: anonymous types declared in an anonymous union are an extension [-Wnested-anon-types]
      struct {
      ^
```

Tools/CMake/AMReXParallelBackends.cmake

@@ -257,7 +257,7 @@ if (AMReX_HIP)
    if(AMReX_ROCTX)
        # To be modernized in the future, please see:
        # https://github.com/ROCm-Developer-Tools/roctracer/issues/56
-       target_include_directories(amrex PUBLIC ${HIP_PATH}/../roctracer/include ${HIP_PATH}/../rocprofiler/include)
+       target_include_directories(amrex SYSTEM PUBLIC ${HIP_PATH}/../roctracer/include ${HIP_PATH}/../rocprofiler/include)
        target_link_libraries(amrex PUBLIC "-L${HIP_PATH}/../roctracer/lib/ -lroctracer64" "-L${HIP_PATH}/../roctracer/lib -lroctx64")
    endif ()
    target_link_libraries(amrex PUBLIC hip::hiprand roc::rocrand roc::rocprim)