375ef42393
On gcc-10 (and gcc-9 -fno-common) build fails as: ``` cc -L../librc -L../libeinfo -O2 -g -std=c99 -Wall -Wextra -Wimplicit -Wshadow \ -Wformat=2 -Wmissing-prototypes -Wmissing-declarations -Wmissing-noreturn \ -Wmissing-format-attribute -Wnested-externs -Winline -Wwrite-strings \ -Wcast-align -Wcast-qual -Wpointer-arith -Wdeclaration-after-statement \ -Wsequence-point -Werror=implicit-function-declaration \ -Wl,-rpath=/lib -o openrc rc.o rc-logger.o rc-misc.o rc-plugin.o _usage.o -lutil -lrc -leinfo -Wl,-Bdynamic -ldl ld: rc-logger.o:/home/slyfox/dev/git/openrc/src/rc/rc-logger.h:16: multiple definition of `rc_logger_pid'; rc.o:openrc/src/rc/rc-logger.h:16: first defined here ld: rc-logger.o:/home/slyfox/dev/git/openrc/src/rc/rc-logger.h:17: multiple definition of `rc_logger_tty'; rc.o:openrc/src/rc/rc-logger.h:17: first defined here ``` gcc-10 will change the default from -fcommon to fno-common: https://gcc.gnu.org/PR85678. The error also happens if CFLAGS=-fno-common passed explicitly. This fixes #348.