[BUG] Last line of a .vmoptions file is silently ignored if it has no trailing newline #464

Describe the bug
The Linux launchers read .vmoptions files with a shell while read loop. read returns false on a final line that has no newline, so that line never reaches the JVM, and the launcher prints no warning. This reproduces every time.

This bites when someone appends -Xmx2g to conf/custom.vmoptions in an editor that does not add a final newline. The engine keeps running with the -Xmx256m from base_includes.vmoptions, which looks like base_includes overriding custom. The JVM uses the last -Xmx it receives, and -Xmx2g never gets there.

To Reproduce

1. Install 4.6.0 with oie_unix_4_6_0.sh.
2. printf '%s' '-Xmx2g' >> conf/custom.vmoptions (no trailing newline)
3. ./oieservice start
4. jcmd <pid> VM.flags | tr ' ' '\n' | grep MaxHeapSize

Expected behavior
MaxHeapSize=2147483648

Actual behavior
MaxHeapSize=268435456, and jcmd <pid> VM.command_line does not list -Xmx2g. After adding the newline (echo >> conf/custom.vmoptions) and restarting, MaxHeapSize is 2147483648.

Environment

• OS: Ubuntu 26.04 (eclipse-temurin:17-jdk container)
• Java: Temurin 17.0.20.1
• OIE 4.6.0, Linux installer

Workaround(s)
End the file with a newline.

Additional context
The generated install4j Unix launchers (oieservice, oieserver, oiecommand) use while read cur_option<&8; do, and server/basedir-includes/oieserver uses while IFS= read -r line; do. Both drop the line. The install4j code is not ours to change, so the proposed fix is a note in the conf/custom.vmoptions comments that the file must end with a newline.

I have not tested oieserver.ps1 or the Windows oieservice.exe. oieserver.ps1 reads with Get-Content, which returns an unterminated last line, so it is probably unaffected.