jdk11_headless: fix the build on amd64

This fixes:

checking user specified JVM feature list...
configure: error: Cannot continue
configure: Unknown JVM features specified: "zgc--enable-headless-only"
configure: The available JVM features are: "aot cds cmsgc compiler1 compiler2 dtrace epsilongc g1gc graal jfr jni-check jvmci jvmti link-time-opt management minimal nmt parallelgc serialgc services static-build vm-structs zero zgc"
configure exiting with result code 1
builder for '/nix/store/1awwzd98crcgxad3srdkv8smhxgiz2qp-openjdk-11.0.1-b13.drv' failed with exit code 1

pkgs/development/compilers/openjdk/11.nix

@@ -67,8 +67,8 @@ let
         # See https://www.mail-archive.com/openembedded-devel@lists.openembedded.org/msg49006.html
         "--with-extra-cflags=-Wno-error=deprecated-declarations -Wno-error=format-contains-nul -Wno-error=unused-result"
     ''
-    + lib.optionalString (architecture == "amd64") "\"--with-jvm-features=zgc\""
-    + lib.optionalString minimal "\"--enable-headless-only\""
+    + lib.optionalString (architecture == "amd64") " \"--with-jvm-features=zgc\""
+    + lib.optionalString minimal " \"--enable-headless-only\""
     + ");"
     # https://bugzilla.redhat.com/show_bug.cgi?id=1306558
     # https://github.com/JetBrains/jdk8u/commit/eaa5e0711a43d64874111254d74893fa299d5716