rtl8188eu: Update README.md and Makefile

I will no longer support the download of zip versions for the source.
whenever there is any change in the source, the user must redo the
entire download and unpacking. This sequence is a lot more complicated
that a simple 'git pull', thus the user skips that step and I have to
deal with complaints about a problem I have already fixed. Now, the
make operation will fail with an error.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>

Makefile

@@ -84,6 +84,8 @@ CONFIG_DRVEXT_MODULE = n
 
 export TopDIR ?= $(shell pwd)
 
+MSG="Directory .git does not exist indicating that you downloaded the source as a zip file. Only the 'git clone' method is now supported."
+
 ########### COMMON  #################################
 
 HCI_NAME = usb
@@ -471,7 +473,10 @@ else
 
 export CONFIG_RTL8188EU = m
 
-all: modules
+all: test modules
+
+test:
+	@if [ !  -e  ./.git ] ; then echo $(MSG); exit 1; fi;
 
 modules:
 	$(MAKE) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) -C $(KSRC) M=$(shell pwd)  modules

README.md

@@ -1,3 +1,22 @@
+IMPORTANT - PLEASE READ:
+
+Beginning on November 4, 2019, I will NO LONGER support people that have downloaded the source
+as a zip file. Using git has much more flexibility. In addition, there is much less liklihood
+that a user will contact me with a problem that is ALREADY fixed.
+
+If your system says that /lib/modules/...../build does not exist, you have not
+installed the kernel headers, you have done it incorrectly, or you are not running
+the kernel for which the headers have been installed. The necessary steps are
+dependent on which distro you are using. Creating a new issue and asking at
+GitHub will not be productive.
+
+Unsolicited E-mail sent to my private address will be ignored!!
+
+If a build fails that previously worked, perform a 'git pull' and retry before
+reporting a problem. As noted, if you had downloaded the source in zip form, then you would
+need to get an entirely new source file. That is why using git, which downloads only the changed
+lines, is required.
+
 rtl8188eu
 =========