use TARGET rather than CORE from Makefile.conf_last to fill in pkgconfig #4900

Job	Run time
build (ubuntu-latest, gfortran, cmake)	41m 33s
build (ubuntu-latest, gfortran, make)	15m 23s
build (ubuntu-latest, flang, cmake)	12m 38s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	5m 43s
build (ubuntu-latest, flang, make)	7m 13s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	10m 3s
build (macos-latest, gfortran, cmake)	25m 7s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	5m 14s
build (macos-latest, gfortran, make)	5m 17s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	4m 44s
msys2 (UCRT64, int32, Release)	17m 7s
msys2 (UCRT64, int64, Release)	17m 7s
msys2 (MINGW32, int32, Release)	18m 9s
msys2 (CLANG64, int32, Release)	17m 19s
msys2 (CLANG64, int64, Release)	16m 6s
msys2 (CLANG32, int32, Release)	9m 55s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	17m 4s
	4h 5m 42s

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