treewide: Use `(( "${NIX_DEBUG:-0}" >= 1) ))` consistently

pkgs/build-support/cc-wrapper/add-hardening.sh

···
   hardeningDisableMap[$flag]=1
 done
 
-if [[ -n "${NIX_DEBUG:-}" ]]; then
+if (( "${NIX_DEBUG:-0}" >= 1 )); then
   printf 'HARDENING: disabled flags:' >&2
   (( "${#hardeningDisableMap[@]}" )) && printf ' %q' "${!hardeningDisableMap[@]}" >&2
   echo >&2
 fi
 
 if [[ -z "${hardeningDisableMap[all]:-}" ]]; then
-  if [[ -n "${NIX_DEBUG:-}" ]]; then
+  if (( "${NIX_DEBUG:-0}" >= 1 )); then
     echo 'HARDENING: Is active (not completely disabled with "all" flag)' >&2;
   fi
   for flag in "${hardeningFlags[@]}"
···
     if [[ -z "${hardeningDisableMap[$flag]:-}" ]]; then
       case $flag in
         fortify)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling fortify >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling fortify >&2; fi
           hardeningCFlags+=('-O2' '-D_FORTIFY_SOURCE=2')
           ;;
         stackprotector)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling stackprotector >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling stackprotector >&2; fi
           hardeningCFlags+=('-fstack-protector-strong' '--param' 'ssp-buffer-size=4')
           ;;
         pie)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling CFlags -fPIE >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling CFlags -fPIE >&2; fi
           hardeningCFlags+=('-fPIE')
           if [[ ! ("$*" =~ " -shared " || "$*" =~ " -static ") ]]; then
-            if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling LDFlags -pie >&2; fi
+            if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling LDFlags -pie >&2; fi
             hardeningCFlags+=('-pie')
             hardeningLDFlags+=('-pie')
           fi
           ;;
         pic)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling pic >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling pic >&2; fi
           hardeningCFlags+=('-fPIC')
           ;;
         strictoverflow)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling strictoverflow >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling strictoverflow >&2; fi
           hardeningCFlags+=('-fno-strict-overflow')
           ;;
         format)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling format >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling format >&2; fi
           hardeningCFlags+=('-Wformat' '-Wformat-security' '-Werror=format-security')
           ;;
         relro)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling relro >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling relro >&2; fi
           hardeningLDFlags+=('-z' 'relro')
           ;;
         bindnow)
-          if [[ -n "${NIX_DEBUG:-}" ]]; then echo HARDENING: enabling bindnow >&2; fi
+          if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling bindnow >&2; fi
           hardeningLDFlags+=('-z' 'now')
           ;;
         *)

pkgs/build-support/cc-wrapper/cc-wrapper.sh

···
 fi
 
 # Optionally print debug info.
-if [ -n "${NIX_DEBUG:-}" ]; then
+if (( "${NIX_DEBUG:-0}" >= 1 )); then
     # Old bash workaround, see ld-wrapper for explanation.
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" ${extraBefore+"${extraBefore[@]}"}  >&2

pkgs/build-support/cc-wrapper/gnat-wrapper.sh

···
 #fi
 
 # Optionally print debug info.
-if [ -n "${NIX_DEBUG:-}" ]; then
+if (( "${NIX_DEBUG:-0}" >= 1 )); then
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" "${extraBefore[@]}"  >&2
     echo "original flags to @prog@:" >&2

pkgs/build-support/cc-wrapper/gnatlink-wrapper.sh

···
 #export NIX_@infixSalt@_LDFLAGS_SET=1
 
 # Optionally print debug info.
-if [ -n "${NIX_DEBUG:-}" ]; then
+if (( "${NIX_DEBUG:-0}" >= 1 )); then
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" "${extraBefore[@]}"  >&2
     echo "original flags to @prog@:" >&2

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

···
 
 
 # Optionally print debug info.
-if [ -n "${NIX_DEBUG:-}" ]; then
+if (( "${NIX_DEBUG:-0}" >= 1 )); then
     # Old bash workaround, see above.
     echo "extra flags before to @prog@:" >&2
     printf "  %q\n" ${extraBefore+"${extraBefore[@]}"}  >&2

pkgs/build-support/cc-wrapper/utils.sh

···
 skip () {
-    if [ -n "${NIX_DEBUG:-}" ]; then
+    if (( "${NIX_DEBUG:-0}" >= 1 )); then
         echo "skipping impure path $1" >&2
     fi
 }

pkgs/stdenv/generic/setup.sh

···
     addToSearchPath PATH "$i/bin"
 done
 
-if [ "${NIX_DEBUG:-}" = 1 ]; then
+if (( "${NIX_DEBUG:-0}" >= 1 )); then
     echo "initial path: $PATH"
 fi
 
···
 
 
 PATH="${_PATH-}${_PATH:+${PATH:+:}}$PATH"
-if [ "${NIX_DEBUG:-}" = 1 ]; then
+if (( "${NIX_DEBUG:-0}" >= 1 )); then
     echo "final path: $PATH"
 fi
 
···
     local -a args=()
 
     for varName in $(awk 'BEGIN { for (v in ENVIRON) if (v ~ /^[a-z][a-zA-Z0-9_]*$/) print v }'); do
-        if [ "${NIX_DEBUG:-}" = "1" ]; then
+        if (( "${NIX_DEBUG:-0}" >= 1 )); then
             printf "@%s@ -> %q\n" "${varName}" "${!varName}"
         fi
         args+=("--subst-var" "$varName")