efivar: Upgrade to tip of trunk

Drop all the patches accepted upstream
Additional important changes it fixes build with lld linker

Following changes are brought over from trunk

* 90e88b2 Allow -a to create a non-existent variable
* 9306e0b Allow passing of hex values to -A
* 328f584 Allow overriding PKG_CONFIG
* cfd686d Revamp efi_well_known_* variable handling
* 914c686 Use off_t instead of off64_t
* dd901c1 Fix IPv4 and IPv6 Device Path printing
* c4138d0 efidp_ipv6_addr: fix gateway size
* bfe9a6b format_ipv6_addr_helper(): fix bad port-printing conditional
* 7c39722 format_ipv6_addr_helper: fix dp_type usage
* 9a5e710 File device paths: don't print "File(" or ")"
* bc65d63 Fix glibc 2.36 build (mount.h conflicts)
* 1f24726 LLD: fix detection and remove not needed workarounds
* 01de743 Set LC_ALL=C to force English output from ld
* 26ad685 Adjust dependency for libefivar and libefiboot objects
* ca48d39 src/Makefile: build util.c separately for makeguids
* b23aba1 Remove deprecated --add-needed linker flag
* 6be2cb1 Fix invalid free in main()
* df09b47 efisecdb: do not free optarg
* cece3ff efisecdb: fix build with musl libc
* aab4e9b Fix the -march issue for riscv64
* 15622b7 Avoid format error on i686
* 28789d1 Add `extern "C"` to headers for easier use by C++
* 197a087 Add -T workaround for GNU ld 2.36

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>