Correct wasm2c example Makefiles (#2426)

- Passing "-lm" into the prereq isn't the correct way add the flag. This correctly adds it to the command.

- The "rot13" example incorrectly assumed that the "rot13.h" file would be generated by the time that "main.c"
  was being compiled, however there is no rule supporting this and it would fail.
  I've also added "rot13.h" to the clean rule.

5 files changed, 14 insertions, 9 deletions

diff --git a/wasm2c/examples/callback/Makefile b/wasm2c/examples/callback/Makefile
index 81ee53ef..ef7abf76 100644
--- a/wasm2c/examples/callback/Makefile
+++ b/wasm2c/examples/callback/Makefile
@@ -1,12 +1,13 @@
 # Use implicit rules for compiling C files.
 CFLAGS=-I../..
+LDLIBS=-lm
 
 all: callback
 
 clean:
 	rm -rf callback callback.wasm callback.c callback.h *.o
 
-callback: main.o callback.o ../../wasm-rt-impl.o ../../wasm-rt-mem-impl.o -lm
+callback: main.o callback.o ../../wasm-rt-impl.o ../../wasm-rt-mem-impl.o
 
 callback.wasm: callback.wat ../../../bin/wat2wasm
 	../../../bin/wat2wasm --debug-names $< -o $@
diff --git a/wasm2c/examples/fac/Makefile b/wasm2c/examples/fac/Makefile
index 623fcfc3..a14a4a6c 100644
--- a/wasm2c/examples/fac/Makefile
+++ b/wasm2c/examples/fac/Makefile
@@ -1,12 +1,13 @@
 # Use implicit rules for compiling C files.
 CFLAGS=-I../..
+LDLIBS=-lm
 
 all: fac
 
 clean:
 	rm -rf fac fac.wasm fac.c *.o
 
-fac: main.o fac.o ../../wasm-rt-impl.o -lm
+fac: main.o fac.o ../../wasm-rt-impl.o
 
 fac.wasm: fac.wat ../../../bin/wat2wasm
 	../../../bin/wat2wasm $< -o $@
diff --git a/wasm2c/examples/fac/fac.wasm b/wasm2c/examples/fac/fac.wasm
deleted file mode 100644
index 711421b6..00000000
--- a/wasm2c/examples/fac/fac.wasm
+++ /dev/null
diff --git a/wasm2c/examples/rot13/Makefile b/wasm2c/examples/rot13/Makefile
index 1d46b3a9..ba93d114 100644
--- a/wasm2c/examples/rot13/Makefile
+++ b/wasm2c/examples/rot13/Makefile
@@ -1,17 +1,20 @@
 # Use implicit rules for compiling C files.
 CFLAGS=-I../..
+LDLIBS=-lm
 
 all: rot13
 
 clean:
-	rm -rf rot13 rot13.wasm rot13.c *.o
+	rm -rf rot13 rot13.wasm rot13.c rot13.h *.o
 
-rot13: main.o rot13.o ../../wasm-rt-impl.o ../../wasm-rt-mem-impl.o -lm
+rot13: main.o rot13.o ../../wasm-rt-impl.o ../../wasm-rt-mem-impl.o
+
+main.o: rot13.h
 
 rot13.wasm: rot13.wat ../../../bin/wat2wasm
 	../../../bin/wat2wasm $< -o $@
 
-rot13.c: rot13.wasm ../../../bin/wasm2c
-	../../../bin/wasm2c $< -o $@ --disable-simd
+rot13.c rot13.h: rot13.wasm ../../../bin/wasm2c
+	../../../bin/wasm2c $< -o rot13.c --disable-simd
 
 .PHONY: all clean
diff --git a/wasm2c/examples/threads/Makefile b/wasm2c/examples/threads/Makefile
index f6eb9998..b671e482 100644
--- a/wasm2c/examples/threads/Makefile
+++ b/wasm2c/examples/threads/Makefile
@@ -1,14 +1,14 @@
 #SANITIZERS=-fsanitize=address -fsanitize=undefined -fno-sanitize-recover=all
 CFLAGS=-I../.. -g -O2 -Wall -Wextra -Wno-unused -Wno-unused-parameter -Wno-array-bounds -Wno-ignored-optimization-argument -Wno-tautological-constant-out-of-range-compare -Wno-infinite-recursion -fno-optimize-sibling-calls -frounding-math -fsignaling-nans ${SANITIZERS} -pthread
-LDFLAGS=${SANITIZERS} -pthread
+LDLIBS=${SANITIZERS} -pthread -lm
 
 all: threads
 
-threads: threads.o sample.o ../../wasm-rt-impl.o ../../wasm-rt-exceptions-impl.o -lm
-
 clean:
 	rm -rf threads sample.wasm sample.c sample.h *.o ../../*.o
 
+threads: threads.o sample.o ../../wasm-rt-impl.o ../../wasm-rt-exceptions-impl.o
+
 sample.wasm: sample.wat ../../../bin/wat2wasm
 	../../../bin/wat2wasm --debug-names $< -o $@