lib, glibc: Get rid of withTLS

glibc removed the underlying flag in 2011 in
83cd14204559abbb52635006832eaf4d2f42514a [1].

This gets us one step closer to fixing #34274: the cross stdenv for
aarch64-unknown-linux-gnu at least evals now.

Thanks to @Dezgeg for doing all the research for this.

[1]: https://sourceware.org/git/?p=glibc.git;a=commit;h=83cd14204559abbb52635006832eaf4d2f42514a

pkgs/development/libraries/glibc/common.nix

@@ -127,7 +127,6 @@ stdenv.mkDerivation ({
     ] ++ lib.optionals withLinuxHeaders [
       "--enable-kernel=3.2.0" # can't get below with glibc >= 2.26
     ] ++ lib.optionals (cross != null) [
-      (if cross.withTLS then "--with-tls" else "--without-tls")
       (if cross ? float && cross.float == "soft" then "--without-fp" else "--with-fp")
     ] ++ lib.optionals (cross != null) [
       "--with-__thread"
@@ -190,8 +189,6 @@ stdenv.mkDerivation ({
     libc_cv_forced_unwind=yes
     libc_cv_c_cleanup=yes
     libc_cv_gnu89_inline=yes
-    # Only due to a problem in gcc configure scripts:
-    libc_cv_sparc64_tls=${if cross.withTLS then "yes" else "no"}
     EOF
 
     export BUILD_CC=gcc