make DEBUG=0 and SYMBOLS=0 behave (nw)

makefile

@@ -235,8 +235,10 @@ SUBTARGET_FULL := $(subst -,_,$(SUBTARGET))
 
 CONFIG = release
 ifdef DEBUG
+ifneq '$(DEBUG)' '0'
 CONFIG := debug
 endif
+endif
 
 ifdef VERBOSE
 MAKEPARAMS += verbose=1
@@ -511,19 +513,18 @@ endif
 
 # profiler defaults to on for DEBUG builds
 ifdef DEBUG
+ifneq '$(DEBUG)' '0'
 ifndef PROFILER
 PROFILER = 1
 endif
 endif
+endif
 
 # allow gprof profiling as well, which overrides the internal PROFILER
 # also enable symbols as it is useless without them
 ifdef PROFILE
 PROFILER =
 SYMBOLS = 1
-ifndef SYMLEVEL
-SYMLEVEL = 1
-endif
 endif
 
 # specify a default optimization level if none explicitly stated
@@ -533,10 +534,14 @@ endif
 
 # set the symbols level
 ifdef SYMBOLS
+PARAMS += --SYMBOLS='$(SYMBOLS)'
+ifneq '$(SYMBOLS)' '0'
 ifndef SYMLEVEL
-SYMLEVEL = 1
 ifdef SOURCES
 SYMLEVEL = 2
+else
+SYMLEVEL = 1
+endif
 endif
 endif
 endif
@@ -559,10 +564,6 @@ PARAMS += --with-benchmarks
 endif
 endif
 
-ifdef SYMBOLS
-PARAMS += --SYMBOLS='$(SYMBOLS)'
-endif
-
 ifdef SYMLEVEL
 PARAMS += --SYMLEVEL='$(SYMLEVEL)'
 endif