doc: Remove links to README.mk-devel

It was removed in f7f6682 ("Update some docs."),
mention doc/build-system-guide.txt instead.

Reviewed-by: Li Wang <[email protected]>
Acked-by: Jan Stancek <[email protected]>
Acked-by: Cyril Hrubis <[email protected]>
Signed-off-by: Petr Vorel <[email protected]>

Author: pevik

INSTALL

@@ -241,7 +241,8 @@ LDFLAGS  - linker flags, e.g. "-L$SYSROOT/usr/lib" "-L$SYSROOT/lib". DO NOT
 LDLIBS   - libraries listed after objects during link, e.g. -lc, -lpthread,
 	   -lltp.
 
-See README.mk-devel for a more terse description of what's available.
+For other variables and more info about the build systems see
+doc/build-system-guide.txt.
 
 Common Issues
 ----------------------

include/mk/config.mk.in

@@ -62,7 +62,7 @@ LDFLAGS			:= @LDFLAGS@
 
 DEBUG_CFLAGS		?= -g
 
-# Please see README.mk-devel about -fstrict-aliasing.
+# for -fstrict-aliasing see doc/build-system-guide.txt
 OPT_CFLAGS		?= -O2 -fno-strict-aliasing -pipe
 
 WCFLAGS			?= -Wall -W @GCC_WARN_OLDSTYLE@