Add os/file.Truncate

[leongross]

Add file.Truncate() to file.go

[10000TB]

any update on next steps ?

[leongross]

CI error does not seem to be related to the Truncate code, maybe another compiler issue? @deadprogram @aykevl, is this related to #3871?

no Go files in D:\a\tinygo\tinygo\tests\testing
ld.lld: error: undefined symbol: notARealFunction
>>> referenced by main
>>>               C:\Users\RUNNER~1\AppData\Local\Temp\tinygo1547056251\main.o
failed to run tool: ld.lld
--- FAIL: TestBuild (0.00s)
    --- FAIL: TestBuild/Host (0.00s)
        --- FAIL: TestBuild/Host/rand.go (36.58s)
            main_test.go:395: output did not match (expected 35 bytes, got 0 bytes):
FAIL
FAIL	github.com/tinygo-org/tinygo	110.872s

[10000TB]

@leongross that seems fixed in 0.29.0