Alias __NR_futex with __NR_futex_time64 for RV32 platform

[shengwen-tw]

Since version 5.1, Linux has dropped several RISC-V 32-bit syscalls by removing __ARCH_WANT_TIME32_SYSCALLS macro, causing the compilation of DirectFB2 to fail on RV32 platform with error of no definition of __NR_futex is declared.

To resolve the issue, this pull request aliases __NR_futex with __NR_futex_time64 as a fallback solution.

[19/181] Compiling C object lib/direct/libdirect-2.0.so.0.0.0.p/os_linux_system.c.o
FAILED: lib/direct/libdirect-2.0.so.0.0.0.p/os_linux_system.c.o 
riscv32-buildroot-linux-gnu-gcc -Ilib/direct/libdirect-2.0.so.0.0.0.p -Ilib/direct -I../../lib/direct -I. -I../.. -Ilib -I../../lib -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -O3 -Wstrict-prototypes -fPIC -pthread '-DMODULEDIR="/usr/local/lib/directfb-2.0-0"' -MD -MQ lib/direct/libdirect-2.0.so.0.0.0.p/os_linux_system.c.o -MF lib/direct/libdirect-2.0.so.0.0.0.p/os_linux_system.c.o.d -o lib/direct/libdirect-2.0.so.0.0.0.p/os_linux_system.c.o -c ../../lib/direct/os/linux/system.c
../../lib/direct/os/linux/system.c: In function ‘direct_futex’:
../../lib/direct/os/linux/system.c:153:19: error: ‘__NR_futex’ undeclared (first use in this function)
  153 |      if (syscall( __NR_futex, uaddr, op, val, timeout, uaddr2, val3 ) < 0)
      |                   ^~~~~~~~~~
../../lib/direct/os/linux/system.c:153:19: note: each undeclared identifier is reported only once for each function it appears in
[36/181] Compiling C object lib/direct/libdirect-2.0.so.0.0.0.p/stream.c.o
ninja: build stopped: subcommand failed.
Assert failed: " meson compile -C build/riscv "

Reference: [1] glibc for 32-bit kernel without __ARCH_WANT_TIME32_SYSCALLS [2] openembedded-core: 0001-fiber-libs-Define-SYS_futex-if-it-does-not-exist.patch

[shengwen-tw]

I'll like to invite @jserv to join the conversation if necessary.