Build with mawk fails on Windows.
I tried to build JDK on WSL2 Debian. Debian uses mawk as an awk Implementation. It failed as below.

$ make images
Building target 'images' in configuration 'windows-x86_64-server-fastdebug'
Compiling up to 1 files for BUILD_TOOLS_HOTSPOT
Compiling up to 8 files for BUILD_TOOLS_LANGTOOLS
Compiling 9 properties into resource bundles for jdk.jshell
Compiling 15 properties into resource bundles for jdk.jdeps
Compiling 17 properties into resource bundles for jdk.javadoc
Generating classes for compiler.properties launcher.properties
Creating hotspot/variant-server/tools/adlc/adlc.exe from 13 file(s)
Compiling up to 2 files for BUILD_JVMTI_TOOLS
Compiling 20 properties into resource bundles for jdk.compiler
nawk: line 1: regular expression compile failed (missing operand)
??_7.*@@6B@
gmake[3]: *** [lib/JvmMapfile.gmk:133: /mnt/c/users/sakat/code/jdk/build/windows-x86_64-server-fastdebug/hotspot/variant-server/libjvm/symbols-objects] Error 2
gmake[3]: *** Waiting for unfinished jobs....
gmake[2]: *** [make/Main.gmk:252: hotspot-server-libs] Error 2
gmake[2]: *** Waiting for unfinished jobs....
Updating support/src.zip

ERROR: Build failed for target 'images' in configuration 'windows-x86_64-server-fastdebug' (exit code 141)

$ awk
Usage: mawk [Options] [Program] [file ...]

Build succeeded when I used gawk instead of mawk.