Define regex_t data structure and write build script

scripts/build.sh

@@ -0,0 +1,11 @@
+cd "$(git rev-parse --show-toplevel)"
+
+CFLAGS="$CFLAGS -std=c11 -pedantic -Wall -Wextra"
+CFLAGS="$CFLAGS -fsanitize=address,undefined"
+CFLAGS="$CFLAGS -O0 -ggdb"
+
+mkdir -p build
+
+# Build library
+clang $CFLAGS -Ilib -c lib/regex.c -o build/regex.o
+ar -crs build/lib.a build/regex.o