Enable custom CFLAGS and LDFLAGS in "Makefile.linux"

[andrei-korshikov]

One patch is better than thousand words:D

diff --git a/src/Makefile.linux b/src/Makefile.linux
index fd765f1..6418b6f 100644
--- a/src/Makefile.linux
+++ b/src/Makefile.linux
@@ -4,8 +4,8 @@ OSTYPE=Linux
 CPUTYPE:=$(shell uname -m)
 HVOPT=-DHV

-CFLAGS=-D$(OSTYPE) -D$(CPUTYPE) $(HVOPT) -Wall -DTAP
-LDFLAGS=-lpthread -lutil
+CFLAGS:=$(CFLAGS) -D$(OSTYPE) -D$(CPUTYPE) $(HVOPT) -Wall -DTAP
+LDFLAGS:=$(LDFLAGS) -lpthread -lutil
 OBJS=vpcs.o \
    daemon.o \
    readline.o \

My use case
I've created vpcs-git package in the Arch Linux User Repository (AUR). During creation, I've got a couple of minor issues:

• ELF file ('usr/bin/vpcs') lacks FULL RELRO, check LDFLAGS
• ELF file ('usr/bin/vpcs') lacks GNU_PROPERTY_X86_FEATURE_1_SHSTK

These issues are really minor and not essential, but… what bad things could happen if custom (system-wide) CFLAGS and LDFLAGS would be enabled?

Related issue
#1