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

pkgs/build-support/bintools-wrapper/default.nix

@@ -243,13 +243,7 @@ stdenv.mkDerivation {
         if [ -e ${libc_lib}/lib/32/ld-linux.so.2 ]; then
           echo ${libc_lib}/lib/32/ld-linux.so.2 > $out/nix-support/dynamic-linker-m32
         fi
-      ''
-      # The dynamic linker is passed in `ldflagsBefore' to allow
-      # explicit overrides of the dynamic linker by callers to ld
-      # (the *last* value counts, so ours should come first).
-      + ''
-        echo -dynamic-linker "$dynamicLinker" >> $out/nix-support/libc-ldflags-before
-    '') + ''
+      '') + ''
       fi
     '')
 

pkgs/build-support/bintools-wrapper/ld-wrapper.sh

@@ -20,6 +20,7 @@ if [ -z "${NIX_BINTOOLS_WRAPPER_FLAGS_SET_@suffixSalt@:-}" ]; then
     source @out@/nix-support/add-flags.sh
 fi
 
+setDynamicLinker=1
 
 # Optionally filter out paths not refering to the store.
 expandResponseParams "$@"
@@ -47,6 +48,11 @@ if [[ "${NIX_ENFORCE_PURITY:-}" = 1 && -n "${NIX_STORE:-}"
             # Our ld is not built with sysroot support (Can we fix that?)
             :
         else
+            if [[ "$p" = -static || "$p" = -static-pie ]]; then
+                # Using a dynamic linker for static binaries can lead to crashes.
+                # This was observed for rust binaries.
+                setDynamicLinker=0
+            fi
             rest+=("$p")
         fi
         n+=1
@@ -63,6 +69,11 @@ extraBefore=(${hardeningLDFlags[@]+"${hardeningLDFlags[@]}"})
 if [ -z "${NIX_LDFLAGS_SET_@suffixSalt@:-}" ]; then
     extraAfter+=($NIX_LDFLAGS_@suffixSalt@)
     extraBefore+=($NIX_LDFLAGS_BEFORE_@suffixSalt@)
+    # By adding dynamic linker to extraBefore we allow the users set their
+    # own dynamic linker as NIX_LD_FLAGS will override earlier set flags
+    if [ "$setDynamicLinker" = 1 ]; then
+        extraBefore+=("-dynamic-linker" "$NIX_DYNAMIC_LINKER_@suffixSalt@")
+    fi
 fi
 
 extraAfter+=($NIX_LDFLAGS_AFTER_@suffixSalt@)
@@ -134,7 +145,7 @@ then
     done
 fi
 
-if [ -e "@out@/nix-support/dynamic-linker-m32" ] && (( "$link32" )); then
+if [[ "$link32" = "0" && "$setDynamicLinker" = 1 && -e "@out@/nix-support/dynamic-linker-m32" ]]; then
     # We have an alternate 32-bit linker and we're producing a 32-bit ELF, let's
     # use it.
     extraAfter+=(