auto/make: Fix various issues with building OTEL

There were at least a couple of issues with building OTEL support.

It only worked with GNU make due to the use of ifeq, even gmake had some
issues.

Debug builds were broken due to trying to pass --debug to cargo which is
the default and isn't a valid option.

This 'fixes' things by doing 'release' builds of OTEL by default.

Passing D=1 to make will generate 'debug' builds but this as previously
with D= etc, only works with GNU make.

Fixes: 9d3dcb8 ("otel: add build tooling to include otel code")
Link: <nginx#1520 (comment)>
Signed-off-by: Andrew Clayton <[email protected]>

auto/make

@@ -21,8 +21,9 @@ AR =			$AR
 
 EXTRA_CFLAGS =
 CFLAGS = 		$NXT_CFLAGS $NXT_CC_OPT $CFLAGS \$(EXTRA_CFLAGS)
-RUST_FLAGS =
-NXT_OTEL_LIB_STATIC =
+
+RUST_FLAGS =		--release
+NXT_OTEL_LIB_STATIC =	$NXT_OTEL_LIB_DIR/target/release/libotel.a
 
 NXT_EXEC_LINK =		$NXT_EXEC_LINK $NXT_LD_OPT
 NXT_SHARED_LOCAL_LINK =	$NXT_SHARED_LOCAL_LINK $NXT_LD_OPT
@@ -63,9 +64,8 @@ D := 0
 
 ifeq (\$D,1)
         CFLAGS += -O0
-        RUST_FLAGS += --debug
-else
-        RUST_FLAGS += --release
+        RUST_FLAGS =
+        NXT_OTEL_LIB_STATIC = $NXT_OTEL_LIB_DIR/target/debug/libotel.a
 endif
 
 # Optionally disable -Werror with
@@ -80,18 +80,6 @@ END
 
 fi
 
-# potentially set otel lib location
-if [ $NXT_OTEL = YES ]; then
-cat << END >> $NXT_MAKEFILE
-
-ifeq (\$D,1)
-	NXT_OTEL_LIB_STATIC = $NXT_OTEL_LIB_DIR/target/debug/libotel.a
-else
-	NXT_OTEL_LIB_STATIC = $NXT_OTEL_LIB_DIR/target/release/libotel.a
-endif
-
-END
-fi
 
 # The include paths list.