nim: unescape "\ " before splitting NIX_LDFLAGS

commit 164ba50fc74b980f77047080b2ae1ea099ae9b27

Author: Emery Hemingway <ehmry@posteo.net>

Date:   Mon Sep 7 14:09:22 2020 +0200

    Load libaries by absolute path on NixOS

    If "nixbuild" is defined then choose dynamic runtime libraries by

    searching $NIX_LDFLAGS at compile-time.

    Fix #15194

diff --git a/lib/pure/dynlib.nim b/lib/pure/dynlib.nim

index f31ae94dd..debed9c07 100644

--- a/lib/pure/dynlib.nim

+    # to enable this behavior by default.

+    #

+    var libDirs = split(getEnv("LD_LIBRARY_PATH"), ':')

+    for flag in split(getEnv("NIX_LDFLAGS")):

+    for flag in split(replace(getEnv("NIX_LDFLAGS"), "\\ ", " ")):

+      if flag.startsWith("-L"):

+        libDirs.add(flag[2..flag.high])

+    for lib in dest: