Curiouser and curiouser.
Or should I say Weirder and weirder?
The reason I wanted to know where the packages are stored is because, the problem came back and I wanted to see what changed in the packages folder.
In folder:
E:\Arduino\Arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.0.4-gcc10.3-1757bed\bin
The file: xtensa-lx106-elf-objdump.exe is missing???
I copied that file from a backup copy of Arduino15, and the compile/link of my sketch works again.
WHAT could be making that file disappear?