Set GOPATH string to empty in build-constants.go
Check for both compile time GOPATH and default GOPATH
while trimming the file path in the stack trace.
Fixes#5741
This is a consolidation effort, avoiding usage
of naked strings in codebase. Whenever possible
use constants which can be repurposed elsewhere.
This also fixes `goconst ./...` reported issues.
kannappanr
Harshavardhana