cmake/pkgconfig: use CMAKE_INSTALL_FULL_* variables #914

Job	Run time
Build static on ubuntu-latest	57s
Build on ubuntu20.04 aarch64 g++-8	9m 25s
Build on ubuntu20.04 aarch64 g++-9	8m 19s
build-macos (macos-latest)	27s
Build on ubuntu20.04 aarch64 g++-10	10m 24s
build-macos (flyci-macos-large-latest-m2)	25s
Build on ubuntu22.04 aarch64 g++-12	9m 28s
Build on ubuntu-20.04 g++-7	1m 27s
Build on ubuntu20.04 aarch64 clang-9	12m 55s
build-windows	2m 30s
Build on ubuntu20.04 aarch64 clang-10	13m 44s
Build on ubuntu-20.04 g++-8	1m 7s
Build on ubuntu22.04 aarch64 clang-14	17m 12s
Build on ubuntu-latest g++-9	1m 13s
Build on ubuntu22.04 armv7 g++	8m 30s
Build on ubuntu22.04 ppc64le g++-12	12m 5s
Build on ubuntu22.04 s390x g++-12	7m 45s
Build on ubuntu-latest g++-10	1m 5s
Build on ubuntu22.04 riscv64 g++-12	8m 20s
Build on ubuntu-20.04 clang-7	1m 12s
Build on ubuntu-20.04 clang-8	59s
Build on ubuntu-20.04 clang-9	1m 2s
Build on ubuntu-20.04 clang-10	1m 7s
Build on ubuntu-20.04 clang-11	53s
Build on ubuntu-latest clang-12	1m 2s
Build on ubuntu-latest clang-13	1m 12s
Build on ubuntu-latest clang-14	1m 37s
	2h 16m 22s

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