[WIP] otel: fix linking on macOS and Ubuntu

The static library is supposed to be specified prior to its
dependencies.
Also, no need to put an otel static library inside libnxt static
library, as we explicitely link unit binary with otel static library
anyway.

This fixes the following build problems:

- macOS:

      Finished `release` profile [optimized] target(s) in 58.07s
    AR     build/lib/libnxt.a
    LD     build/sbin/unitd
  ld: archive member 'libotel.a' not a mach-o file in '/private/tmp/unit-20241219-8965-yb46xp/build/lib/libnxt.a'
  clang: error: linker command failed with exit code 1 (use -v to see invocation)

- Ubuntu 22 (./configure --otel):

  LD     build/sbin/unitd
cc -Wl,-E  -o build/sbin/unitd -pipe -fPIC -fvisibility=hidden -fno-strict-overflow -funsigned-char -std=gnu11 -O -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -fno-strict-aliasing -Wmissing-prototypes -Werror -g    \
	build/src/nxt_main.o  build/lib/libnxt.a \
	-lm -lrt  -lpthread   \
                      \
                    -lpcre2-8 -lssl -lcrypto src/otel/target/release/libotel.a
/usr/bin/ld: src/otel/target/release/libotel.a(reqwest-97d1376dfb77d784.reqwest.cb371ce8e1e3945e-cgu.04.rcgu.o): in function `core::ptr::drop_in_place<alloc::vec::Vec<reqwest::tls::Certificate>>':
reqwest.cb371ce8e1e3945e-cgu.04:(.text._ZN4core3ptr69drop_in_place$LT$alloc..vec..Vec$LT$reqwest..tls..Certificate$GT$$GT$17h9b62679cc7161be5E+0x30): undefined reference to `X509_free'

auto/make

@@ -157,11 +157,12 @@ libnxt:	$NXT_BUILD_DIR/lib/$NXT_LIB_SHARED $NXT_BUILD_DIR/lib/$NXT_LIB_STATIC
 $NXT_BUILD_DIR/lib/$NXT_LIB_SHARED: \$(NXT_LIB_OBJS) \$(NXT_OTEL_LIB_LOC)
 	\$(PP_LD) \$@
 	\$(v)\$(NXT_SHARED_LOCAL_LINK) -o \$@ \$(NXT_LIB_OBJS) \\
-		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS \$(NXT_OTEL_LIB_LOC)
+		\$(NXT_OTEL_LIB_LOC) \\
+		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS
 
-$NXT_BUILD_DIR/lib/$NXT_LIB_STATIC: \$(NXT_LIB_OBJS) \$(NXT_OTEL_LIB_LOC)
+$NXT_BUILD_DIR/lib/$NXT_LIB_STATIC: \$(NXT_LIB_OBJS)
 	\$(PP_AR) \$@
-	\$(v)$NXT_STATIC_LINK \$@ \$(NXT_LIB_OBJS) \$(NXT_OTEL_LIB_LOC)
+	\$(v)$NXT_STATIC_LINK \$@ \$(NXT_LIB_OBJS)
 
 $NXT_BUILD_DIR/lib/$NXT_LIB_UNIT_STATIC: \$(NXT_LIB_UNIT_OBJS) \\
 		$NXT_BUILD_DIR/share/pkgconfig/unit.pc \\
@@ -379,7 +380,8 @@ $NXT_BUILD_DIR/sbin/$NXT_DAEMON:	$NXT_BUILD_DIR/lib/$NXT_LIB_STATIC \\
 	\$(PP_LD) \$@
 	\$(v)\$(NXT_EXEC_LINK) -o \$@ \$(CFLAGS) \\
 		\$(NXT_OBJS) $NXT_BUILD_DIR/lib/$NXT_LIB_STATIC \\
-		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS \$(NXT_OTEL_LIB_LOC)
+		\$(NXT_OTEL_LIB_LOC) \\
+		$NXT_LIBM $NXT_LIBS $NXT_LIB_AUX_LIBS
 
 END