Bug#893023: librsl FTBFS with flex 2.6.4-6

[Adrian Bunk]

Source: librsl
Version: 1.43-1.2
Severity: serious

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/librsl.html

...
/bin/bash ../libtool  --tag=CC   --mode=link gcc  -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -static -Wl,-z,relro -o any_to_gif any_to_gif.o -L/usr/lib -lmfhdf -ldf -ljpeg -lz -lm -lfl ../.libs/librsl.a  -L/usr/lib -lmfhdf -ldf -ljpeg -lz -lm -lfl
libtool: link: gcc -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wl,-z -Wl,relro -o any_to_gif any_to_gif.o  -L/usr/lib ../.libs/librsl.a /usr/lib/libmfhdf.so /usr/lib/libdf.so -ljpeg -lz -lm -lfl
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libfl.so: undefined reference to `yylex'
collect2: error: ld returned 1 exit status
make[3]: *** [Makefile:487: any_to_gif] Error 1