On Windows CI, skip installing Boost except for amalgamation target #772

Job	Run time
valgrind (clang, -O1, valgrind-ct-full)	1h 5m 35s
clang-tidy	1h 17m 20s
Sanitizers (sanitizer, msvc, windows-2022, ninja)	34m 9s
valgrind (clang, -O2, valgrind-ct-full)	1h 0m 17s
TLS-Anvil (server)	31m 31s
Sanitizers (sanitizer, gcc, ubuntu-24.04)	49m 1s
valgrind (clang, -O3, valgrind-ct-full)	58m 15s
valgrind (gcc, -O1, valgrind-ct-full)	1h 20m 15s
Cross (cross-arm32, gcc, ubuntu-24.04)	27m 10s
valgrind (gcc, -O2, valgrind-ct-full)	1h 3m 8s
PQ/T TLS 1.3	34s
valgrind (gcc, -O3, valgrind-ct-full)	57m 37s
Cross (cross-alpha, gcc, ubuntu-24.04)	7m 43s
valgrind (clang, valgrind-full)	1h 41m 29s
Cross (cross-hppa64, gcc, ubuntu-24.04)	30m 1s
valgrind (clang, -Os, valgrind-ct-full)	1h 9m 40s
Cross (cross-m68k, gcc, ubuntu-24.04)	24m 43s
valgrind (gcc, -Os, valgrind-ct)	1h 35m 18s
Cross (cross-mips, gcc, ubuntu-24.04)	24m 9s
Cross (cross-ppc32, gcc, ubuntu-24.04)	44s
Cross (cross-sh4, gcc, ubuntu-24.04)	21m 41s
Cross (cross-sparc64, gcc, ubuntu-24.04)	29m 54s
Cross (cross-riscv64, gcc, ubuntu-24.04)	9m 32s
Cross (cross-s390x, gcc, ubuntu-24.04)	17m 45s
Cross (cross-android-arm64-amalgamation, clang, ubuntu-24.04)	48s
Cross (cross-arm64-amalgamation, gcc, ubuntu-24.04)	13m 24s
Cross (emscripten, emcc, macos-14)	6m 54s
Cross (sde, gcc, ubuntu-24.04)	15m 31s
	17h 54m 8s

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