uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

pkgs/development/compilers/nim/nixbuild.patch

@@ -0,0 +1,51 @@
+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
++++ b/lib/pure/dynlib.nim
+@@ -56,6 +56,9 @@
+ 
+ import strutils
+ 
++when defined(nixbuild):
++  import os
++
+ type
+   LibHandle* = pointer ## a handle to a dynamically loaded library
+ 
+@@ -95,6 +98,25 @@ proc libCandidates*(s: string, dest: var seq[string]) =
+       libCandidates(prefix & middle & suffix, dest)
+   else:
+     add(dest, s)
++  when defined(nixbuild):
++    # Nix doesn't have a global library directory so
++    # load libraries using an absolute path if one
++    # can be derived from NIX_LDFLAGS.
++    #
++    # During Nix/NixOS packaging the line "define:nixbuild"
++    # should be appended to the ../../config/nim.cfg file
++    # to enable this behavior by default.
++    #
++    var libDirs = split(getEnv("LD_LIBRARY_PATH"), ':')
++    for flag in split(getEnv("NIX_LDFLAGS")):
++      if flag.startsWith("-L"):
++        libDirs.add(flag[2..flag.high])
++    for lib in dest:
++      for dir in libDirs:
++        let abs = dir / lib
++        if existsFile(abs):
++          dest = @[abs]
++          return
+ 
+ proc loadLibPattern*(pattern: string, globalSymbols = false): LibHandle =
+   ## loads a library with name matching `pattern`, similar to what `dlimport`