[GR-44775] Fix incorrect calculation of "other data".

[graalvmbot]

This PR fixes a bug that caused "other data" to be miscalculated and show a negative number when debug info is used on Windows or on Linux when objcopy is unavailable. The PR also includes some minor improvements.

Before:

[8/8] Creating image...       [****]
  10.09MB (43.92%) for code area:    14,037 compilation units
  12.26MB (53.33%) for image heap:  146,829 objects and 56 resources
   7.39MB (32.15%) for debug info generated in 6.5s
-6757322.00B (-29.41%) for other data
  22.98MB in total

After:

[8/8] Creating image...       [***]
  10.09MB (43.92%) for code area:    14,037 compilation units
  12.26MB (53.33%) for image heap:  146,830 objects and 56 resources
   7.39MB (32.15%) for debug info generated in 4.6s
 630.61kB ( 2.74%) for other data
  22.98MB in total