This commit deduplicates libgcc-related boilerplate which appears in
every version of our gcc expression, by moving it into libgcc.nix.
I will be submitting a separate PR which changes this boilerplate,
but that PR will be much easier to review if I can make the change
in just one place.
Meanwhile, *this* commit has no effect on eval:
$ for A in 10 11 12 13 4.8 4.9 6 7 8 9; do nix-instantiate . -A gcc$(echo $A | tr -d .); done 2>/dev/null | sort | tee before
/nix/store/1a37lnzpnz0dhm3lphiy2gcdrxgqa7ma-gcc-wrapper-4.8.5.drv
/nix/store/5szdivc8il0c3g94dq4wqnq5j77a9h6p-gcc-wrapper-11.4.0.drv
/nix/store/bmmc717wmnp1j2xkd3if5dfxicnflvn5-gcc-wrapper-7.5.0.drv
/nix/store/fc1ggpixv3wqcazchhl2hnn5zl5ds30l-gcc-wrapper-13.1.0.drv
/nix/store/j9c2b20w35r3ag5nxmklhagbwsgjhds2-gcc-wrapper-4.9.4.drv
/nix/store/nq7q57bxmsk2g457wr4b9449as3f216w-gcc-wrapper-12.3.0.drv
/nix/store/sqmkkfapzykapcs4azvxm83n786ga7q1-gcc-wrapper-10.4.0.drv
/nix/store/vxnz30i23mkl4ldsq485kxn7q0p2y4nf-gcc-wrapper-8.5.0.drv
/nix/store/yfhv0bv15cg5kj2xsb9fcgb6pdlw42v0-gcc-wrapper-6.5.0.drv
/nix/store/yi5gr75pb6kddnll10jg25hhndhkba7s-gcc-wrapper-9.5.0.drv
$ for A in 10 11 12 13 4.8 4.9 6 7 8 9; do nix-instantiate . -A gcc$(echo $A | tr -d .); done | sort | tee after
/nix/store/1a37lnzpnz0dhm3lphiy2gcdrxgqa7ma-gcc-wrapper-4.8.5.drv
/nix/store/5szdivc8il0c3g94dq4wqnq5j77a9h6p-gcc-wrapper-11.4.0.drv
/nix/store/bmmc717wmnp1j2xkd3if5dfxicnflvn5-gcc-wrapper-7.5.0.drv
/nix/store/fc1ggpixv3wqcazchhl2hnn5zl5ds30l-gcc-wrapper-13.1.0.drv
/nix/store/j9c2b20w35r3ag5nxmklhagbwsgjhds2-gcc-wrapper-4.9.4.drv
/nix/store/nq7q57bxmsk2g457wr4b9449as3f216w-gcc-wrapper-12.3.0.drv
/nix/store/sqmkkfapzykapcs4azvxm83n786ga7q1-gcc-wrapper-10.4.0.drv
/nix/store/vxnz30i23mkl4ldsq485kxn7q0p2y4nf-gcc-wrapper-8.5.0.drv
/nix/store/yfhv0bv15cg5kj2xsb9fcgb6pdlw42v0-gcc-wrapper-6.5.0.drv
/nix/store/yi5gr75pb6kddnll10jg25hhndhkba7s-gcc-wrapper-9.5.0.drv
$ diff -u after before
$
