[GR-39407] Add support for NATIVE_IMAGE_OPTIONS environment variable.

[graalvmbot]

This PR adds support for the NATIVE_IMAGE_OPTIONS environment variable, which allows users and tools to pass additional arguments via the environment. Similar to JAVA_TOOL_OPTIONS, the value of the environment variable is prepended to the options supplied to native-image.

Here's an example that shows how NATIVE_IMAGE_OPTIONScan be used to turn on the quick build mode:

$ NATIVE_IMAGE_OPTIONS="-Ob" native-image -m jdk.httpserver
========================================================================================================================
GraalVM Native Image: Generating 'jdk.httpserver' (executable)...
========================================================================================================================
[1/8] Initializing...                                                                                    (5.0s @ 0.19GB)
 Java version: 22+18, vendor version: Oracle GraalVM 22-dev+18.1
 Graal compiler: optimization level: b, target machine: x86-64-v3, PGO: off
 C compiler: gcc (linux, x86_64, 13.2.0)
 Garbage collector: Serial GC (max heap size: 80% of RAM)
 1 user-specific feature(s):
 - com.oracle.svm.thirdparty.gson.GsonFeature
------------------------------------------------------------------------------------------------------------------------
 Picked up NATIVE_IMAGE_OPTIONS:
 - '-Ob'
------------------------------------------------------------------------------------------------------------------------
...

To allow previous build steps to add additional options (as opposed to overwriting them), consider using:

• NATIVE_IMAGE_OPTIONS="${NATIVE_IMAGE_OPTIONS} -Ob" native-image ... to append -Ob; or
• NATIVE_IMAGE_OPTIONS="-Ob ${NATIVE_IMAGE_OPTIONS}" native-image ... to prepend -Ob.