fix unaryop round build with old glibc

[nihui]

No description provided.

[codecov-commenter]

Codecov Report

Merging #4963 (d30bcb7) into master (cb674ac) will decrease coverage by 0.01%.
Report is 6 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4963      +/-   ##
==========================================
- Coverage   94.90%   94.90%   -0.01%     
==========================================
  Files         776      776              
  Lines      226448   226446       -2     
==========================================
- Hits       214910   214908       -2     
  Misses      11538    11538              

Files Changed	Coverage Δ
src/layer/arm/unaryop_arm.cpp	99.30% <ø> (ø)
src/layer/arm/unaryop_arm_asimdhp.cpp	99.62% <ø> (ø)
src/layer/loongarch/unaryop_loongarch.cpp	99.44% <ø> (ø)
src/layer/mips/unaryop_mips.cpp	99.45% <ø> (ø)
src/layer/unaryop.cpp	98.98% <ø> (ø)
src/layer/x86/unaryop_x86.cpp	99.59% <ø> (ø)

... and 1 file with indirect coverage changes