Blender Finder: support multi-line output of blender --version

When compiled without OpenColorIO, Blender will first complain "Color
management: Error could not find role data role." before showing the
actual version number. This is now handled by looking for a "Blender "
prefix instead of just returning the first line of output.

This has as a side-effect that when no such line can be found, we know
it's not Blender, and thus an error can be returned (instead of the
version of whatever binary was being run).

internal/find_blender/find_blender.go

@@ -15,7 +15,10 @@ import (
 	"github.com/rs/zerolog/log"
 )
 
-var ErrNotAvailable = errors.New("not available on this platform")
+var (
+	ErrNotAvailable = errors.New("not available on this platform")
+	ErrNotBlender   = errors.New("not a Blender executable")
+)
 
 // blenderVersionTimeout is how long `blender --version` is allowed to take,
 // before timing out. This can be much slower than expected, when loading
@@ -104,10 +107,12 @@ func getBlenderVersion(ctx context.Context, commandline string) (string, error)
 	}
 
 	version := string(stdoutStderr)
-	lines := strings.SplitN(version, "\n", 2)
-	if len(lines) > 0 {
-		version = lines[0]
+	lines := strings.Split(version, "\n")
+	for idx := range lines {
+		line := strings.TrimSpace(lines[idx])
+		if strings.HasPrefix(line, "Blender ") {
+			return line, nil
+		}
 	}
-
-	return strings.TrimSpace(version), nil
+	return "", fmt.Errorf("%s: %w", commandline, ErrNotBlender)
 }