remove the trailing new line in NIX_LD

[contrun]

There is a trailing new line in the dynamic-linker file. This should be removed.

$ nix eval --impure --expr 'with import <nixpkgs> {}; builtins.readFile "${stdenv.cc}/nix-support/dynamic-linker"'
"/nix/store/0c7c96gikmzv87i7lv3vq5s1cmfjd6zf-glibc-2.31-74/lib/ld-linux-x86-64.so.2\n"

$ nix eval --impure --expr 'with import <nixpkgs> {}; lib.fileContents "${stdenv.cc}/nix-support/dynamic-linker"'
"/nix/store/0c7c96gikmzv87i7lv3vq5s1cmfjd6zf-glibc-2.31-74/lib/ld-linux-x86-64.so.2"

[Mic92]

Does not really matter actually because we remove it here as well: https://github.com/Mic92/nix-ld/blob/55086c739b537e8257b7714aeffecaf7271932a6/src/nix-ld.c#L249

[contrun]

I see. Thanks for merging this.

I copied the previous snippet to environment.sessionVariables, and encountered a pam error.

Okt 17 19:18:35 ssg sudo[3193941]: pam_env(sudo:session): Unterminated quoted string: "/nix/store/mij848h2x5wiqkwhg027byvmf9x3gx7y-glibc-2.33-50/lib/ld-linux-x86-64.so.2
Okt 17 19:18:35 ssg sudo[3193941]: pam_env(sudo:session): pam_putenv: delete non-existent entry; "

Because the generated /etc/pam/environment is like this

NIX_LD   DEFAULT="/nix/store/mij848h2x5wiqkwhg027byvmf9x3gx7y-glibc-2.33-50/lib/ld-linux-x86-64.so.2
"

I guess using lib.fileContents will save a little of someone else's life.