pritest: Redirecting incorrect sys/signal.h to signal.h

[InterLinked1]

When musl is used, such as on Alpine Linux, there is a warning about redirecting sys/signal.h to signal.h:

gcc  -shared -Wl,-hlibpri.so.1.4  -o libpri.so.1.4 copy_string.o pri.o q921.o prisched.o q931.o pri_aoc.o pri_cc.o pri_facility.o asn1_primitive.o rose.o rose_address.o rose_etsi_aoc.o rose_etsi_cc.o rose_etsi_diversion.o rose_etsi_ect.o rose_etsi_mwi.o rose_other.o rose_q931.o rose_qsig_aoc.o rose_qsig_cc.o rose_qsig_ct.o rose_qsig_diversion.o rose_qsig_mwi.o rose_qsig_name.o version.o
/sbin/ldconfig -n .
ln -sf libpri.so.1.4 libpri.so
gcc -g  -Wall -Werror -Wstrict-prototypes -Wmissing-prototypes -Wno-zero-length-bounds -Wno-stringop-overflow -fPIC  -O2  -MD -MT pridump.o -MF .pridump.o.d -MP -c -o pridump.o pridump.c
gcc -o pridump pridump.o -L. -lpri -g  -Wall -Werror -Wstrict-prototypes -Wmissing-prototypes -Wno-zero-length-bounds -Wno-stringop-overflow -fPIC  -O2 
gcc -g  -Wall -Werror -Wstrict-prototypes -Wmissing-prototypes -Wno-zero-length-bounds -Wno-stringop-overflow -fPIC  -O2  -MD -MT pritest.o -MF .pritest.o.d -MP -c -o pritest.o pritest.c
In file included from pritest.c:44:
/usr/include/sys/signal.h:1:2: error: #warning redirecting incorrect #include <sys/signal.h> to <signal.h> [-Werror=cpp]
    1 | #warning redirecting incorrect #include <sys/signal.h> to <signal.h>
      |  ^~~~~~~
cc1: all warnings being treated as errors
make: *** [Makefile:192: pritest.o] Error 1