treewide: JAVA_HOME may not always be defined

pkgs/development/compilers/adoptopenjdk-bin/jdk-darwin-base.nix

@@ -37,7 +37,7 @@ let cpuName = stdenv.hostPlatform.parsed.cpu.name;
 
     # Set JAVA_HOME automatically.
     cat <<EOF >> $out/nix-support/setup-hook
-    if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+    if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
     EOF
   '';
 

pkgs/development/compilers/adoptopenjdk-bin/jdk-linux-base.nix

@@ -54,7 +54,7 @@ let result = stdenv.mkDerivation rec {
 
     # Set JAVA_HOME automatically.
     cat <<EOF >> "$out/nix-support/setup-hook"
-    if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+    if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
     EOF
   '';
 

pkgs/development/compilers/graalvm/default.nix

@@ -270,7 +270,7 @@ in rec {
       # Set JAVA_HOME automatically.
       mkdir -p $out/nix-support
       cat <<EOF > $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
       EOF
     '';
     postFixup = openjdk.postFixup or null;

pkgs/development/compilers/graalvm/enterprise-edition.nix

@@ -72,7 +72,7 @@ let
       # Set JAVA_HOME automatically.
       mkdir -p $out/nix-support
       cat <<EOF > $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
       EOF
     '';
 

pkgs/development/compilers/openjdk/11.nix

@@ -106,7 +106,7 @@ let
       # Set JAVA_HOME automatically.
       mkdir -p $out/nix-support
       cat <<EOF > $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out/lib/openjdk; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out/lib/openjdk; fi
       EOF
     '';
 

pkgs/development/compilers/openjdk/8.nix

@@ -231,7 +231,7 @@ let
       # Set JAVA_HOME automatically.
       mkdir -p $out/nix-support
       cat <<EOF > $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out/lib/openjdk; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out/lib/openjdk; fi
       EOF
     '';
 

pkgs/development/compilers/openjdk/darwin/11.nix

@@ -44,7 +44,7 @@ let
 
       # Set JAVA_HOME automatically.
       cat <<EOF >> $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
       EOF
     '';
 

pkgs/development/compilers/openjdk/darwin/8.nix

@@ -44,7 +44,7 @@ let
 
       # Set JAVA_HOME automatically.
       cat <<EOF >> $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
       EOF
     '';
 

pkgs/development/compilers/openjdk/darwin/default.nix

@@ -44,7 +44,7 @@ let
 
       # Set JAVA_HOME automatically.
       cat <<EOF >> $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
       EOF
     '';
 

pkgs/development/compilers/openjdk/default.nix

@@ -114,7 +114,7 @@ let
       # Set JAVA_HOME automatically.
       mkdir -p $out/nix-support
       cat <<EOF > $out/nix-support/setup-hook
-      if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out/lib/openjdk; fi
+      if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out/lib/openjdk; fi
       EOF
     '';
 

pkgs/development/compilers/oraclejdk/jdk-linux-base.nix

@@ -156,7 +156,7 @@ let result = stdenv.mkDerivation rec {
 
     # Set JAVA_HOME automatically.
     cat <<EOF >> $out/nix-support/setup-hook
-    if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+    if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
     EOF
   '';
 

pkgs/development/compilers/zulu/8.nix

@@ -58,7 +58,7 @@ in stdenv.mkDerivation {
 
     # Set JAVA_HOME automatically.
     cat <<EOF >> $out/nix-support/setup-hook
-    if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+    if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
     EOF
   '';
 

pkgs/development/compilers/zulu/default.nix

@@ -55,7 +55,7 @@ in stdenv.mkDerivation {
 
     # Set JAVA_HOME automatically.
     cat <<EOF >> $out/nix-support/setup-hook
-    if [ -z "\$JAVA_HOME" ]; then export JAVA_HOME=$out; fi
+    if [ -z "\''${JAVA_HOME-}" ]; then export JAVA_HOME=$out; fi
     EOF
   '';
 

pkgs/development/tools/build-managers/apache-ant/1.9.nix

@@ -46,14 +46,14 @@ stdenv.mkDerivation {
       # JRE by looking for java.  The latter allows just the JRE to be
       # used with (say) ECJ as the compiler.  Finally, allow the GNU
       # JVM.
-      if [ -z "\$JAVA_HOME" ]; then
+      if [ -z "\''${JAVA_HOME-}" ]; then
           for i in javac java gij; do
               if p="\$(type -p \$i)"; then
                   export JAVA_HOME="\$(${coreutils}/bin/dirname \$(${coreutils}/bin/dirname \$(${coreutils}/bin/readlink -f \$p)))"
                   break
               fi
           done
-          if [ -z "\$JAVA_HOME" ]; then
+          if [ -z "\''${JAVA_HOME-}" ]; then
               echo "\$0: cannot find the JDK or JRE" >&2
               exit 1
           fi

pkgs/development/tools/build-managers/apache-ant/default.nix

@@ -46,14 +46,14 @@ stdenv.mkDerivation {
       # JRE by looking for java.  The latter allows just the JRE to be
       # used with (say) ECJ as the compiler.  Finally, allow the GNU
       # JVM.
-      if [ -z "\$JAVA_HOME" ]; then
+      if [ -z "\''${JAVA_HOME-}" ]; then
           for i in javac java gij; do
               if p="\$(type -p \$i)"; then
                   export JAVA_HOME="\$(${coreutils}/bin/dirname \$(${coreutils}/bin/dirname \$(${coreutils}/bin/readlink -f \$p)))"
                   break
               fi
           done
-          if [ -z "\$JAVA_HOME" ]; then
+          if [ -z "\''${JAVA_HOME-}" ]; then
               echo "\$0: cannot find the JDK or JRE" >&2
               exit 1
           fi