compiler: use full paths for debug info source files

Firstly introduced in 9871dc8. Leads
to failing tests on Windows with the following error:
```
2022-02-09T09:39:31.3307626Z panic: Rel: can't make D:\a\neo-go\neo-go\pkg\interop\neogointernal\syscall.go relative to C:\Users\RUNNER~1\AppData\Local\Temp\TestContractInitAndCompile1998984267\001\testcontract [recovered]
2022-02-09T09:39:31.3308830Z 	panic: Rel: can't make D:\a\neo-go\neo-go\pkg\interop\neogointernal\syscall.go relative to C:\Users\RUNNER~1\AppData\Local\Temp\TestContractInitAndCompile1998984267\001\testcontract
2022-02-09T09:39:31.3309285Z
2022-02-09T09:39:31.3309390Z goroutine 302 [running]:
2022-02-09T09:39:31.3309725Z testing.tRunner.func1.2({0x14dbfe0, 0xc00051bdb0})
2022-02-09T09:39:31.3310187Z 	C:/hostedtoolcache/windows/go/1.17.6/x64/src/testing/testing.go:1209 +0x36c
2022-02-09T09:39:31.3310538Z testing.tRunner.func1()
2022-02-09T09:39:31.3310937Z 	C:/hostedtoolcache/windows/go/1.17.6/x64/src/testing/testing.go:1212 +0x3b6
2022-02-09T09:39:31.3311285Z panic({0x14dbfe0, 0xc00051bdb0})
2022-02-09T09:39:31.3311689Z 	C:/hostedtoolcache/windows/go/1.17.6/x64/src/runtime/panic.go:1047 +0x266
2022-02-09T09:39:31.3312319Z github.com/nspcc-dev/neo-go/pkg/compiler.(*codegen).fillDocumentInfo.func1(0xc0002d0b40)
2022-02-09T09:39:31.3312885Z 	D:/a/neo-go/neo-go/pkg/compiler/analysis.go:240 +0x34d
2022-02-09T09:39:31.3313397Z go/token.(*FileSet).Iterate(0xc0000a69c0, 0xc0004898b0)
2022-02-09T09:39:31.3313839Z 	C:/hostedtoolcache/windows/go/1.17.6/x64/src/go/token/position.go:463 +0xde
2022-02-09T09:39:31.3314404Z github.com/nspcc-dev/neo-go/pkg/compiler.(*codegen).fillDocumentInfo(0xc0002e4d20)
2022-02-09T09:39:31.3314947Z 	D:/a/neo-go/neo-go/pkg/compiler/analysis.go:236 +0x97
2022-02-09T09:39:31.3315530Z github.com/nspcc-dev/neo-go/pkg/compiler.(*codegen).compile(0xc0002e4d20, 0xc00009a690, 0xc000101540)
2022-02-09T09:39:31.3316064Z 	D:/a/neo-go/neo-go/pkg/compiler/codegen.go:2088 +0x192
2022-02-09T09:39:31.3316563Z github.com/nspcc-dev/neo-go/pkg/compiler.codeGen(0xc00009a690)
2022-02-09T09:39:31.3317066Z 	D:/a/neo-go/neo-go/pkg/compiler/codegen.go:2167 +0x7cd
2022-02-09T09:39:31.3317679Z github.com/nspcc-dev/neo-go/pkg/compiler.CompileWithOptions({0xc0000435e0, 0x62}, {0x0, 0x0}, 0xc0004bcf70)
2022-02-09T09:39:31.3318233Z 	D:/a/neo-go/neo-go/pkg/compiler/compiler.go:225 +0xde
2022-02-09T09:39:31.3318804Z github.com/nspcc-dev/neo-go/pkg/compiler.CompileAndSave({0xc0000435e0, 0x62}, 0xc0004bcf70)
2022-02-09T09:39:31.3319353Z 	D:/a/neo-go/neo-go/pkg/compiler/compiler.go:241 +0x3a5
2022-02-09T09:39:31.3319889Z github.com/nspcc-dev/neo-go/cli/smartcontract.contractCompile(0xc0004e42c0)
2022-02-09T09:39:31.3320456Z 	D:/a/neo-go/neo-go/cli/smartcontract/smart_contract.go:520 +0xc2d
2022-02-09T09:39:31.3320873Z github.com/urfave/cli.HandleAction({0x14b6fa0, 0x17b8d60}, 0x7)
2022-02-09T09:39:31.3321344Z 	C:/Users/runneradmin/go/pkg/mod/github.com/urfave/cli@v1.22.5/app.go:524 +0xf4
2022-02-09T09:39:31.3321931Z github.com/urfave/cli.Command.Run({{0x16460d2, 0x7}, {0x0, 0x0}, {0x0, 0x0, 0x0}, {0x166fe9e, 0x27}, {0x0, ...}, ...}, ...)
2022-02-09T09:39:31.3322443Z 	C:/Users/runneradmin/go/pkg/mod/github.com/urfave/cli@v1.22.5/command.go:173 +0xc09
2022-02-09T09:39:31.3322894Z github.com/urfave/cli.(*App).RunAsSubcommand(0xc0000b7340, 0xc0004e4000)
2022-02-09T09:39:31.3323375Z 	C:/Users/runneradmin/go/pkg/mod/github.com/urfave/cli@v1.22.5/app.go:405 +0x106c
2022-02-09T09:39:31.3323852Z github.com/urfave/cli.Command.startApp({{0x1647536, 0x8}, {0x0, 0x0}, {0x0, 0x0, 0x0}, {0x1671070, 0x28}, {0x0, ...}, ...}, ...)
2022-02-09T09:39:31.3324365Z 	C:/Users/runneradmin/go/pkg/mod/github.com/urfave/cli@v1.22.5/command.go:372 +0x108c
2022-02-09T09:39:31.3324838Z github.com/urfave/cli.Command.Run({{0x1647536, 0x8}, {0x0, 0x0}, {0x0, 0x0, 0x0}, {0x1671070, 0x28}, {0x0, ...}, ...}, ...)
2022-02-09T09:39:31.3325327Z 	C:/Users/runneradmin/go/pkg/mod/github.com/urfave/cli@v1.22.5/command.go:102 +0xe8c
2022-02-09T09:39:31.3325744Z github.com/urfave/cli.(*App).Run(0xc000323880, {0xc0004237a0, 0xb, 0x12})
2022-02-09T09:39:31.3326198Z 	C:/Users/runneradmin/go/pkg/mod/github.com/urfave/cli@v1.22.5/app.go:277 +0xa8c
2022-02-09T09:39:31.3326770Z github.com/nspcc-dev/neo-go/cli.(*executor).run(0xc0000709c0, {0xc0004237a0, 0xb, 0x12})
2022-02-09T09:39:31.3327275Z 	D:/a/neo-go/neo-go/cli/executor_test.go:273 +0x3a5
2022-02-09T09:39:31.3327812Z github.com/nspcc-dev/neo-go/cli.(*executor).Run(0x14aa020, 0xc000493950, {0xc0004237a0, 0xb, 0x12})
2022-02-09T09:39:31.3328324Z 	D:/a/neo-go/neo-go/cli/executor_test.go:263 +0x10f
2022-02-09T09:39:31.3328844Z github.com/nspcc-dev/neo-go/cli.TestContractInitAndCompile(0xc0001d69c0)
2022-02-09T09:39:31.3329377Z 	D:/a/neo-go/neo-go/cli/contract_test.go:155 +0x147f
2022-02-09T09:39:31.3329694Z testing.tRunner(0xc0001d69c0, 0x17b8be8)
2022-02-09T09:39:31.3330123Z 	C:/hostedtoolcache/windows/go/1.17.6/x64/src/testing/testing.go:1259 +0x230
2022-02-09T09:39:31.3330470Z created by testing.(*T).Run
2022-02-09T09:39:31.3330862Z 	C:/hostedtoolcache/windows/go/1.17.6/x64/src/testing/testing.go:1306 +0x727
2022-02-09T09:39:31.3331325Z FAIL	github.com/nspcc-dev/neo-go/cli	5.552s

```

pkg/compiler/analysis.go

@@ -5,7 +5,6 @@ import (
 	"go/ast"
 	"go/token"
 	"go/types"
-	"path/filepath"
 	"strings"
 
 	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
@@ -235,10 +234,6 @@ func (c *codegen) fillDocumentInfo() {
 	fset := c.buildInfo.config.Fset
 	fset.Iterate(func(f *token.File) bool {
 		filePath := f.Position(f.Pos(0)).Filename
-		filePath, err := filepath.Rel(c.buildInfo.config.Dir, filePath)
-		if err != nil {
-			panic(err)
-		}
 		c.docIndex[filePath] = len(c.documents)
 		c.documents = append(c.documents, filePath)
 		return true