contrib: use rm -f instead of dash prefix

This is more silent and avoid messages like:
rm: cannot remove 'CMakeCache.txt': No such file or directory
make: [.mysofa] Error 1 (ignored)

contrib/src/fluidlite/rules.mak

@@ -25,7 +25,7 @@ fluidlite: fluidlite-$(FLUID_HASH).tar.xz .sum-fluidlite
 	$(MOVE)
 
 .fluidlite: fluidlite toolchain.cmake
-	-cd $< && rm CMakeCache.txt
+	cd $< && rm -f CMakeCache.txt
 	cd $< && $(HOSTVARS) $(CMAKE)
 	cd $< && $(MAKE) install
 	touch $@

contrib/src/mysofa/rules.mak

@@ -24,7 +24,7 @@ mysofa: libmysofa-$(MYSOFA_VERSION).tar.gz .sum-mysofa
 	$(MOVE)
 
 .mysofa: mysofa toolchain.cmake
-	-cd $< && rm CMakeCache.txt
+	cd $< && rm -f CMakeCache.txt
 	cd $< && $(HOSTVARS) $(CMAKE) -DBUILD_TESTS=OFF -DBUILD_SHARED_LIBS=OFF
 	cd $< && $(MAKE) install
 	touch $@

contrib/src/projectM/rules.mak

@@ -35,7 +35,7 @@ endif
 DEPS_projectM = glew $(DEPS_glew)
 
 .projectM: projectM toolchain.cmake
-	-cd $< && rm CMakeCache.txt
+	cd $< && rm -f CMakeCache.txt
 	cd $< && $(HOSTVARS) $(CMAKE) \
 		-DINCLUDE-PROJECTM-LIBVISUAL:BOOL=OFF \
 		-DDISABLE_NATIVE_PRESETS:BOOL=ON \

contrib/src/spatialaudio/rules.mak

@@ -21,7 +21,7 @@ spatialaudio: spatialaudio-$(SPATIALAUDIO_VERSION).tar.bz2 .sum-spatialaudio
 	$(MOVE)
 
 .spatialaudio: spatialaudio toolchain.cmake
-	-cd $< && rm CMakeCache.txt
+	cd $< && rm -f CMakeCache.txt
 	cd $< && $(HOSTVARS) $(CMAKE) -DMYSOFA_ROOT_DIR=$(PREFIX) -DHAVE_MIT_HRTF=OFF
 	cd $< && $(MAKE) install
 	touch $@