$ make

• download sqlite-amalgamation from https://www.sqlite.org/download.html
• extract all files from the ZIP
• (install MinGW if you haven't done so already, Debian/Ubuntu package: mingw32)
• run CC=i586-mingw32msvc-gcc CFLAGS=-I/path/to/sqlite-amalgamation make
• rename hunupper.so to hunupper.dll

sqlite> .load ./hunupper.so
sqlite> select HUNUPPER("árvíztűrő tükörfúrógép");
ÁRVÍZTŰRŐ TÜKÖRFÚRÓGÉP

The whole project is available under MIT license, see LICENSE.txt.