Under-linking issue: -lm

[nehaljwani]

Issue

# Create a dev environment with gts and deps
$ conda create -p ./dev -c conda-forge gts glib

# Activate the dev environment
$ conda activate ./dev

# Create a very small reproducible example to highlight the issue
$ cat <<EOF > example.c
#include <gts.h>

int main()
{
	GtsVector normalisedAxis;
        gts_matrix_rotate(NULL, normalisedAxis, 1.0);
        return 0;
}
EOF

# Compile the example, and that leads to link failures:
$ gcc \
  $(PKG_CONFIG_PATH=$CONDA_PREFIX/lib/pkgconfig pkg-config -cflags gts) \
  $(PKG_CONFIG_PATH=$CONDA_PREFIX/lib/pkgconfig pkg-config --libs gts) \
  example.c 
/usr/bin/ld: /tmp/nwani_1686490018/dev/lib/libgts.so: undefined reference to `sincos'
/usr/bin/ld: /tmp/nwani_1686490018/dev/lib/libgts.so: undefined reference to `atan2'
/usr/bin/ld: /tmp/nwani_1686490018/dev/lib/libgts.so: undefined reference to `exp'
/usr/bin/ld: /tmp/nwani_1686490018/dev/lib/libgts.so: undefined reference to `cos'
/usr/bin/ld: /tmp/nwani_1686490018/dev/lib/libgts.so: undefined reference to `log'
/usr/bin/ld: /tmp/nwani_1686490018/dev/lib/libgts.so: undefined reference to `sqrt'
collect2: error: ld returned 1 exit status