Fix Linux ARM64 crash caused by missing fontconfig in cross-compile sysroot

[mattleibow]

Summary

This PR fixes the hard crash on Linux ARM64 (issue #3369) by adding the fontconfig runtime library to ALL cross-compile Docker sysroots.

Root Cause Analysis

The ARM64 cross-compile Docker was only downloading libfontconfig1-dev which provides:

• Headers (fontconfig.h, etc.)
• Static library (libfontconfig.a)

The actual shared library (libfontconfig.so.1.12.0) is in the runtime package (libfontconfig1), not the dev package.

Why the build succeeded but runtime failed

1. The ninja build includes -lfontconfig in the link command
2. The linker finds libfontconfig.so symlink, but it points to a non-existent file
3. The resulting libSkiaSharp.so is missing libfontconfig.so.1 from its DT_NEEDED entries
4. At runtime, fontconfig is loaded implicitly via freetype
5. fontconfig calls uuid_generate_random() which requires libuuid
6. CRASH: undefined symbol: uuid_generate_random

Comparison: x64 vs ARM64 before fix

x64 (native build) - has fontconfig:

DT_NEEDED: libpthread.so.0, libfontconfig.so.1, libdl.so.2, libm.so.6, libc.so.6

ARM64 (cross-compile) - missing fontconfig:

DT_NEEDED: libpthread.so.0, libdl.so.2, libm.so.6, libc.so.6

ARM64 after fix

DT_NEEDED: libpthread.so.0, libfontconfig.so.1, libdl.so.2, libm.so.6, libc.so.6

The Fix

Download both packages when setting up the cross-compile sysroot:

• libfontconfig1-dev - headers and static library
• libfontconfig1 - actual shared library

Files changed:

• scripts/Docker/debian/clang-cross/10/Dockerfile (arm, arm64, x86, riscv64)
• scripts/Docker/debian/clang-cross/11/Dockerfile (same fix for consistency)
• scripts/Docker/debian/clang-cross/12/Dockerfile (same fix for consistency)
• scripts/Docker/debian/clang-cross/13/Dockerfile (loongarch64)

Testing

✅ Built ARM64 with fix - fontconfig now appears in DT_NEEDED
✅ Tested font operations (SKTypeface.FromFamilyName, DrawText) on ARM64 Docker
✅ No more undefined symbol: uuid_generate_random crash

Related Issues

This fix also resolves:

• [BUG] libSkiaSharp.so: undefined symbol: uuid_generate_random on Debian Bookworm ARM64 #3272 - Same uuid_generate_random error on Debian ARM64
• [BUG] undefined symbol exception thrown in linux ARM-64 #3436 - Both FT_Get_BDF_Property and uuid_generate_random on ARM64

Fixes #3369
Fixes #3272
Fixes #3436

[github-actions]

Triage Summary

Labels will be applied to indicate issues related to reliability on Linux ARM64, the SkiaSharp library, and its backend functionalities.

This issue does not appear to be marked as a regression, but it highlights a critical reliability issue.

Additional remarks:

• The severity of the hard crash on Linux ARM64 could potentially impact users significantly.

Detailed Summary and Actions

Summary of the triage:

• The issue signifies a hard crash on the Linux ARM64 platform.
• It is relevant to the reliability of the application, particularly in the SkiaSharp library.
• The problem reflects aspects of both the SkiaSharp backend and its association with Android due to shared architecture.

Summary of the actions that will be performed:

Action	Item	Description
Apply Label	tenet/reliability	The issue describes a hard crash on Linux ARM64, indicating a reliability problem.
Apply Label	os/Linux	The issue mentions a hard crash occurring specifically on Linux ARM64.
Apply Label	area/SkiaSharp	The specifics of the issue relate to a hard crash in the SkiaSharp library.
Apply Label	backend/SkiaSharp	The issue references the SkiaSharp 3.119.0 version, marking it relevant to that specific backend.
Apply Label	backend/Android	The investigation involves Linux ARM64, relevant to the Android platform as they share architecture.

This entire triage process was automated by AI and mistakes may have been made. Please let us know so we can continue to improve.