refactor: libc - share printf, split the float path, fix relink deps

programs/src/lua/Makefile

@@ -39,9 +39,13 @@ CFLAGS := \
     -isystem ../../include/libc \
     -isystem $(shell $(CC) -print-file-name=include)
 
+# -u _pf_putfloat forces liblibc.a's optional printf_float.o member to be
+# linked: Lua formats floats (%.14g in lobject.c, %f/%e/%g via string.format),
+# and vsnprintf only references the float conversions weakly.
 LDFLAGS := \
     -nostdlib \
     -Wl,--gc-sections \
+    -Wl,-u,_pf_putfloat \
     -T ../../link.ld
 
 CORE_SRCS := \