x/perf: build failures due to C compiler warnings in github.com/mattn/go-sqlite3

[bcmills]

2020-09-18T15:55:09-d949658/solaris-amd64-oraclerel

# github.com/mattn/go-sqlite3
sqlite3-binding.c: In function ‘sqlite3SelectNew.isra’:
sqlite3-binding.c:114528:10: warning: function may return address of local variable [-Wreturn-local-addr]
114528 |   return pNew;
       |          ^~~~
sqlite3-binding.c:114488:10: note: declared here
114488 |   Select standin;
       |          ^~~~~~~
go build github.com/mattn/go-sqlite3: C compiler warning promoted to error on Go builders

2020-09-18T15:55:09-d949658/openbsd-386-68
2020-09-18T15:55:09-d949658/openbsd-amd64-68

# github.com/mattn/go-sqlite3
sqlite3-binding.c:104476:38: warning: implicit conversion from 'long long' to 'double' changes value from 9223372036854775806 to 9223372036854775808 [-Wimplicit-int-float-conversion]
sqlite3-binding.c:104478:46: warning: implicit conversion from 'long long' to 'double' changes value from 9223372036854775806 to 9223372036854775808 [-Wimplicit-int-float-conversion]
go build github.com/mattn/go-sqlite3: C compiler warning promoted to error on Go builders

CC @golang/release via #11811

[bcmills]

These failures appear to have started as of CL 222540, which suggests that those builders were previously using the vendor directory, although I'm not sure how. (The default -mod=vendor trigger is go 1.14 or higher in the go.mod file, but the go.mod file for this module is only go 1.11.)

[bcmills]

The implicit conversion seems to be mattn/go-sqlite3#867, which AFAICT is fixed upstream at head.

[bcmills]

The function may return address of local variable warning seems to be mattn/go-sqlite3#803 / mattn/go-sqlite3#822.

[bcmills]

Fixed by CL 275192.