fix: S390x compatability

[navaneeswar1011]

Description

This PR fixes a build failure encountered while compiling Dgraph on IBM s390x architecture caused by a datatype mismatch in the disk metrics module.

Problem

During compilation, the build fails in x/disk_metrics_linux.go due to architecture-specific type differences in the Linux syscall.Statfs_t structure.

The existing implementation performs arithmetic operations using mixed types:

disk.All = s.Frsize * int64(s.Blocks-reservedBlocks)
disk.Free = s.Frsize * int64(s.Bavail)

On s390x architecture, the datatype definitions for Frsize, Blocks, and Bavail differ from architectures such as x86_64, causing a compile-time type mismatch.

Fix

Added explicit type conversion for Frsize to ensure consistent datatype handling during arithmetic operations.

Updated code:

disk.All = int64(s.Frsize) * int64(s.Blocks-reservedBlocks)
disk.Free = int64(s.Frsize) * int64(s.Bavail)

Validation Performed

The fix was validated by building and testing on multiple architectures:

• s390x (RHEL VM) → Build completed successfully
• x86_64 (Ubuntu VM) → Build completed successfully
• ARM64 (macOS) → Build completed successfully

Additionally verified:

• Successful startup of both Zero and Alpha services
• CRUD operations executed successfully after build validation

Impact

• Resolves architecture-specific build failure on IBM s390x
• Improves cross-platform compatibility
• No functional logic changes introduced
• No impact observed on existing supported architectures

Checklist

• The PR title follows the
  Conventional Commits syntax, leading
  with fix:, feat:, chore:, ci:, etc.
• Code compiles correctly and linting (via trunk) passes locally
• Tests added for new functionality, or regression tests for bug fixes added as applicable

[matthewmcneely]

These changes are out of scope. Please revert. I will address in another PR