if it helps i went with

git clone https://github.com/ampl/gsl.git

cd gsl

mkdir -p build/emscripten && cd build/emscripten

emcmake cmake ../.. -DBUILDLIBS="cblas;const;err;ieee-utils;monte;multimin;permutation;rstat;spmatrix;utils;blas;cdf;deriv;fft;integration;movstat;multiroots;poly;siman;statistics;vector;block;cheb;dht;filter;interpolation;multifit;multiset;qrng;sort;sum;wavelet;bspline;diff;fit;linalg;multifit_nlinear;ntuple;randist;spblas;bst;combination;gsl;matrix;multilarge;ode-initval;rng;specfunc;sys;complex;eigen;histogram;min;multilarge_nlinear;ode-initval2;roots;splinalg" \ 
    -DNO_AMPL_BINDINGS=1 \
    -DCMAKE_BUILD_TYPE=Release \
    -DCMAKE_C_FLAGS="-O2 -s USE_PTHREADS=0" \
    -DCMAKE_EXE_LINKER_FLAGS="-s ALLOW_MEMORY_GROWTH=1" \
    -DCMAKE_INSTALL_PREFIX=.

emmake make
emmake make install