Restore toolchain env sources so CI can find GraalVM

nativeCompile failed on the runners with "Cannot find a Java installation
matching {languageVersion=25, vendor=GraalVM Community}".

Gradle's toolchain auto-detection only reads JAVA_HOME, and the native job
overwrites that with the JDK 21 it uses to compile the jars, so GRAALVM_HOME
— set by setup-graalvm — was never read by anything. The build kept working
locally through an entirely different path: mise exports ASDF_DATA_DIR and
Gradle discovers its installs through the asdf provider, so the missing
setting was invisible outside CI.

Auto-provisioning stays off deliberately. It cannot produce a usable GraalVM
anyway: unpacking a downloaded JDK does not preserve the symlink GraalVM
ships at bin/native-image, and nativeCompile then dies on an empty file.

Author: abashev

gradle.properties

@@ -7,3 +7,13 @@ org.gradle.jvmargs=--add-exports jdk.compiler/com.sun.tools.javac.api=ALL-UNNAME
   --add-exports jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED \
   --add-exports jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED
 palantir.native.formatter=true
+
+# Where Gradle looks for JDKs. Auto-detection only reads JAVA_HOME, and CI overwrites that with
+# the JDK 21 used for the jars — so without this line GraalVM stays invisible and nativeCompile
+# fails with "Cannot find a Java installation ... vendor=GraalVM Community". Locally these are
+# unset and mise's installs are found through Gradle's asdf provider instead.
+#
+# Auto-provisioning stays off deliberately: it cannot produce a working GraalVM anyway, because
+# unpacking a downloaded JDK does not preserve the symlink GraalVM ships at bin/native-image.
+org.gradle.java.installations.auto-download=false
+org.gradle.java.installations.fromEnv=JDK21_HOME,GRAALVM_HOME