MT#55283 don't use automatic variable in prereq

As per [1], quote:

It’s very important that you recognize the limited scope in which
automatic variable values are available: they only have values within
the recipe. In particular, you cannot use them anywhere within the
target list of a rule; they have no value there and will expand to the
empty string. Also, they cannot be accessed directly within the
prerequisite list of a rule. A common mistake is attempting to use $@
within the prerequisites list; this will not work.

Based on the patch by S-P Chan <shihping.chan@gmail.com>

[1] https://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html

closes #1754

Thanks: S-P Chan <shihping.chan@gmail.com>
Change-Id: Ia5f9d7a75f04d9533afaace8ed49cc222e4307a8
Ref: https://github.com/sipwise/rtpengine/issues/1754

lib/common.Makefile

@@ -53,7 +53,7 @@ t38.c:		spandsp_logging.h
 %.strhash.c:	%.c ../utils/const_str_hash
 	../utils/const_str_hash "$<" < "$<" > "$@"
 
-$(BUILD_TEST_ALTS):	../lib/$(@:.h=-*)
+$(BUILD_TEST_ALTS):	$(wildcard ../lib/$(subst .h,-*,$(BUILD_TEST_ALTS)))
 	../utils/build_test_wrapper "$@" 2> /dev/null
 
 .PHONY: all debug clean install