Drop "isGlibc", but keep isMusl.

gnu "abi" doesn't mean glibc (mingw, apparently).

lib/systems/default.nix

@@ -26,8 +26,7 @@ rec {
       libc =
         /**/ if final.isDarwin then "libSystem"
         else if final.isMinGW  then "msvcrt"
-        else if final.isLinux && final.isGlibc then "glibc"
-        else if final.isLinux && final.isMusl  then "musl"
+        else if final.isMusl  then "musl"
         else if final.isLinux /* default */    then "glibc"
         # TODO(@Ericson2314) think more about other operating systems
         else                        "native/impure";

lib/systems/inspect.nix

@@ -35,7 +35,6 @@ rec {
     MinGW        = { kernel = kernels.windows; abi = abis.gnu; };
 
     Musl         = with abis; map (a: { abi = a; }) [ musl musleabi musleabihf ];
-    Glibc        = with abis; map (a: { abi = a; }) [ gnu gnueabi gnueabihf ];
   };
 
   matchAnyAttrs = patterns: