nim c -r main.nim doesn't recompile if nim binary changes or gets updated

[timotheecour]

this is a follow up for #11719 regarding the new "smart run" feature

nim c -r main.nim doesn't recompile if nim binary changes (or if the nim binary gets updated)

Example

nim_temp1 c -r main.nim
nim_temp2 c -r main.nim # should recompile because nim_temp2 !=nim_temp1

# main.nim
static: echo "CT:" & NimVersion
echo NimVersion

Current Output

CT:0.20.99
0.20.99
0.20.99

Expected Output

CT:0.20.99
0.20.99
CT:0.20.99
0.20.99

Possible Solution

• the generated nimcache/main.json should keep track of the nim binary path
• if the nim binary path changes OR the nim binary is newer than the generated main.json file, then recompile, just like any other dependency

Additional Information

$ nim -v
Nim Compiler Version 0.20.99 [MacOSX: amd64]
Compiled at 2019-07-16
Copyright (c) 2006-2019 by Andreas Rumpf

git hash: 44d80dd86373b9ba41051428948eae30ed97acd3
active boot switches: -d:release