ossfuzz: add spng include dir to compiler flags

Author: concatime

tests/ossfuzz.sh

@@ -19,12 +19,14 @@ ar rcs libspng_static.a *.o
 
 $CXX $CXXFLAGS -std=c++11 \
     $SRC/libspng/tests/spng_read_fuzzer.c \
+    -I$SRC/libspng/spng \
     -DSPNGT_HAVE_FMEMOPEN=1 \
     -o $OUT/spng_read_fuzzer \
     $LIB_FUZZING_ENGINE $SRC/libspng/build/libspng_static.a $SRC/zlib/build/libz.a
 
 $CXX $CXXFLAGS -std=c++11 -I$SRC/zlib/build -I$SRC/zlib \
     $SRC/libspng/tests/spng_read_fuzzer.c \
+    -I$SRC/libspng/spng \
     -DSPNGT_HAVE_FMEMOPEN=1 \
     -o $OUT/spng_read_fuzzer_structure_aware \
     -include $SRC/fuzzer-test-suite/libpng-1.2.56/png_mutator.h \