Bug 284929 – Build fails on architectures without SYS_futex

• Status: NEW
• Component: ANGLE

[Khem Raj]

__NR_futex is not defines by newer architectures e.g. arc, riscv32 as
they only have 64bit variant of time_t. Glibc defines SYS_futex interface based
on __NR_futex, since this is used in applications, such applications start
to fail to build for these newer architectures. This patch defines a
fallback to alias __NR_futex to __NR_futex_tim64 so SYS_futex keeps
working

Currently builds on riscv32 e.g. fails like below.

| /mnt/b/yoe/master/build/tmp/work/riscv32-yoe-linux/webkitgtk/2.46.4/webkitgtk-2.46.4/Source/ThirdParty/ANGLE/src/common/SimpleMutex.cpp:36:13: error: use of undeclared identifier 'SYS_futex'
|    36 |     syscall(SYS_futex, addr, op, val, nullptr, nullptr, val3);
|       |             ^
| 1 error generated.

[Radar WebKit Bug Importer]

<rdar://problem/142046679>