[indic/khmer] Remove use of global constructors
Alternative woul have been to resurrect F_COMBINE that I removed in
70136a78cb9eda244767f8e8a3d30d0f3c569d01
But this does it for now. I'm not sure why check-static-inits.sh didn't
catch this before. Clang -Weverything bot did:
CXX libharfbuzz_la-hb-ot-shape-complex-indic.lo
hb-ot-shape-complex-indic.cc:99:1: warning: declaration requires a global constructor [-Wglobal-constructors]
indic_features[] =
^
1 warning generated.
CXX libharfbuzz_la-hb-ot-shape-complex-khmer.lo
hb-ot-shape-complex-khmer.cc:36:1: warning: declaration requires a global constructor [-Wglobal-constructors]
khmer_features[] =
^
1 warning generated.