Introduce new fatcosmocc command

This new script is an alternative to the `cosmocc` command. It's still a
work in progress. It abstracts all the gory details of building separate
copies of your executable and then running the apelink.com program.

build/definitions.mk

@@ -83,7 +83,6 @@ COMPILE = build/bootstrap/compile.com -V9 -P4096 $(QUOTA)
 COMMA := ,
 PWD := $(shell build/bootstrap/pwd.com)
 
-IGNORE := $(shell $(ECHO) -2 ♥cosmo)
 IGNORE := $(shell $(MKDIR) $(TMPDIR))
 
 ifneq ($(findstring aarch64,$(MODE)),)
@@ -188,6 +187,10 @@ DEFAULT_COPTS ?=							\
 	-fno-asynchronous-unwind-tables
 
 ifeq ($(ARCH), x86_64)
+# Microsoft says "[a]ny memory below the stack beyond the red zone
+# [note: Windows defines the x64 red zone size as 0] is considered
+# volatile and may be modified by the operating system at any time."
+# https://devblogs.microsoft.com/oldnewthing/20190111-00/?p=100685
 DEFAULT_COPTS +=							\
 	-mno-red-zone							\
 	-mno-tls-direct-seg-refs
@@ -201,6 +204,9 @@ ifeq ($(ARCH), aarch64)
 # - Cosmopolitan Libc uses x28 for thread-local storage because Apple
 #   forbids us from using tpidr_el0 too.
 #
+# - Cosmopolitan currently lacks an implementation of the runtime
+#   libraries needed by the -moutline-atomics flag
+#
 DEFAULT_COPTS +=							\
 	-ffixed-x18							\
 	-ffixed-x28							\