Moved -Werror flag to CI only

The most useful part of -Werror is preventing code from being
merged that has warnings. However it is annoying for users who may have
different compilers with different warnings. Limiting -Werror to CI only
covers the main concern about warnings without limiting users.

.travis.yml

@@ -1,20 +1,23 @@
+env:
+    - CFLAGS=-Werror
+
 script:
     # make sure example can at least compile
     - sed -n '/``` c/,/```/{/```/d; p;}' README.md > test.c &&
-      CFLAGS='
+      make all size CFLAGS+="
         -Duser_provided_block_device_read=NULL
         -Duser_provided_block_device_prog=NULL
         -Duser_provided_block_device_erase=NULL
         -Duser_provided_block_device_sync=NULL
-        -include stdio.h -Werror' make all size
+        -include stdio.h"
 
     # run tests
     - make test QUIET=1
 
     # run tests with a few different configurations
-    - CFLAGS="-DLFS_READ_SIZE=1   -DLFS_PROG_SIZE=1"       make test QUIET=1
-    - CFLAGS="-DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512"     make test QUIET=1
-    - CFLAGS="-DLFS_BLOCK_COUNT=1023 -DLFS_LOOKAHEAD=2048" make test QUIET=1
+    - make test QUIET=1 CFLAGS+="-DLFS_READ_SIZE=1      -DLFS_PROG_SIZE=1"
+    - make test QUIET=1 CFLAGS+="-DLFS_READ_SIZE=512    -DLFS_PROG_SIZE=512"
+    - make test QUIET=1 CFLAGS+="-DLFS_BLOCK_COUNT=1023 -DLFS_LOOKAHEAD=2048"
 
     # self-host with littlefs-fuse for fuzz test
     - make -C littlefs-fuse

Makefile

@@ -14,15 +14,15 @@ TEST := $(patsubst tests/%.sh,%,$(wildcard tests/test_*))
 SHELL = /bin/bash -o pipefail
 
 ifdef DEBUG
-CFLAGS += -O0 -g3
+override CFLAGS += -O0 -g3
 else
-CFLAGS += -Os
+override CFLAGS += -Os
 endif
 ifdef WORD
-CFLAGS += -m$(WORD)
+override CFLAGS += -m$(WORD)
 endif
-CFLAGS += -I.
-CFLAGS += -std=c99 -Wall -pedantic
+override CFLAGS += -I.
+override CFLAGS += -std=c99 -Wall -pedantic
 
 
 all: $(TARGET)

tests/test.py

@@ -33,8 +33,7 @@ def generate(test):
         pass
 
 def compile():
-    os.environ['CFLAGS'] = os.environ.get('CFLAGS', '') + ' -Werror'
-    subprocess.check_call(['make', '--no-print-directory', '-s'], env=os.environ)
+    subprocess.check_call(['make', '--no-print-directory', '-s'])
 
 def execute():
     subprocess.check_call(["./lfs"])