rocr/amd_core_dump: Fix "arithmetic on a pointer to void"

A recent patch introduced a build failure when building with Clang:

    [ 65%] Building CXX object runtime/hsa-runtime/CMakeFiles/hsa-runtime64.dir/libamdhsacode/amd_core_dump.cpp.o
    […]/runtime/hsa-runtime/libamdhsacode/amd_core_dump.cpp:271:29: error: arithmetic on a pointer to void
      271 |       read = pread(fd_, buf + done, buf_size - done,
          |                         ~~~ ^
    1 error generated.

This patch fixes this by making sure the "void *" pointer is converting
to "char *" before doing arithmetic on it.

Change-Id: Ib1663ed30abce76e05f06d042975eccd7d729823

runtime/hsa-runtime/libamdhsacode/amd_core_dump.cpp

@@ -268,7 +268,8 @@ struct LoadSegmentBuilder : public SegmentBuilder {
     size_t done = 0;
     ssize_t read;
     do {
-      read = pread(fd_, buf + done, buf_size - done, offset + done);
+      read = pread(fd_, static_cast<char *>(buf) + done, buf_size - done,
+                   offset + done);
 
       if (read == -1 && errno != EINTR) {
         perror("Failed to read GPU memory");