Remove duplicate do-test target from devel/libexecinfo

I noticed that devel/libexecinfo/Makefile defines a do-test target *twice*.
The second version is the same as the first, but the overly long line is
broken into two lines.

This diff eliminates the version that exceeds 80 columns (and was redefined
away anyway by the 2nd).

ok?

--Kurt

Index: Makefile
===================================================================
RCS file: /cvs/ports/devel/libexecinfo/Makefile,v
retrieving revision 1.25
diff -u -p -r1.25 Makefile
--- Makefile 12 Jul 2019 20:44:38 -0000 1.25
+++ Makefile 3 Jan 2020 03:33:22 -0000
@@ -40,9 +40,6 @@ post-install:
${PREFIX}/bin/backtrace_test

do-test:
- ${SETENV} LD_LIBRARY_PATH=${WRKSRC}/libbacktrace ${WRKSRC}/examples/backtrace_test
-
-do-test:
${SETENV} LD_LIBRARY_PATH=${WRKSRC}/libbacktrace \
${WRKSRC}/examples/backtrace_test