bintools-wrapper: skip dynamic linker for static binaries

Currently we set dynamic-linker unconditionally. This breaks
however some static binaries i.e. rust binaries linked against musl.
There is no reason we should set an elf interpreter for static binaries
hence this is skipped if `-static` or `-static-pie` is either passed to
our cc or ld wrapper.

pkgs/build-support/bintools-wrapper/add-flags.sh

@@ -3,6 +3,7 @@ var_templates_list=(
     NIX_IGNORE_LD_THROUGH_GCC
     NIX_LDFLAGS
     NIX_LDFLAGS_BEFORE
+    NIX_DYNAMIC_LINKER
     NIX_LDFLAGS_AFTER
     NIX_LDFLAGS_HARDEN
     NIX_HARDENING_ENABLE
@@ -25,6 +26,10 @@ if [ -e @out@/nix-support/libc-ldflags ]; then
     NIX_LDFLAGS_@suffixSalt@+=" $(< @out@/nix-support/libc-ldflags)"
 fi
 
+if [ -z "$NIX_DYNAMIC_LINKER_@suffixSalt@" ] && [ -e @out@/nix-support/dynamic-linker ]; then
+    NIX_DYNAMIC_LINKER_@suffixSalt@="$(< @out@/nix-support/dynamic-linker)"
+fi
+
 if [ -e @out@/nix-support/libc-ldflags-before ]; then
     NIX_LDFLAGS_BEFORE_@suffixSalt@="$(< @out@/nix-support/libc-ldflags-before) $NIX_LDFLAGS_BEFORE_@suffixSalt@"
 fi