folly manifest: promote openssl to universal dep + force Apple ar/ranlib on darwin

Summary:
Two unrelated cleanups to the folly manifest.

1. Promote openssl from per-OS `[dependencies.os=*]` entries to the universal `[dependencies]` block. folly uses OpenSSL on every supported platform: openssl's manifest is `builder=nop` on linux/freebsd (resolves via the distro's openssl-devel package) and builds from source on darwin/windows. Listing it once at the top is simpler and lets `install-system-deps --recursive` pick it up uniformly. This also removes a stale comment claiming the manifest format can't express "system dep is sufficient" -- that capability now exists via the `nop` builder + `[debs]`/`[rpms]` declarations in the openssl manifest.

2. Force `CMAKE_AR=/usr/bin/ar` and `CMAKE_RANLIB=/usr/bin/ranlib` on darwin. When folly is built with Homebrew LLVM clang on macOS (used by the wheels CI to pick up C++23 features that AppleClang doesn't have), CMake otherwise picks up Homebrew's llvm-ar, which writes BSD-style archives with a "/" symbol-table member that Apple's classic linker cannot parse for empty archives. Several folly portability libraries have no source files on darwin and produce exactly such empty archives, which then fail to link. Apple's tools always emit archives the system linker accepts, and AppleClang already uses /usr/bin/ar by default, so this is a no-op for AppleClang folly users.

Reviewed By: bigfootjon

Differential Revision: D104428959

fbshipit-source-id: 3390a631e533c34095f5db8ebb1fdd5ccc2f5ebb

Author: r-barnes

build/fbcode_builder/manifests/folly

@@ -23,25 +23,12 @@ double-conversion
 fast_float
 fmt
 lz4
+openssl
 snappy
 zstd
-# no openssl or zlib in the linux case, why?
-# these are usually installed on the system
-# and are the easiest system deps to pull in.
-# In the future we want to be able to express
-# that a system dep is sufficient in the manifest
-# for eg: openssl and zlib, but for now we don't
-# have it.
-
-# macOS doesn't expose the openssl api so we need
-# to build our own.
-[dependencies.os=darwin]
-openssl
 
-# Windows has neither openssl nor zlib, so we get
-# to provide both
+# Windows has no zlib, so we get to provide it
 [dependencies.os=windows]
-openssl
 zlib
 
 [dependencies.os=linux]
@@ -71,6 +58,20 @@ BOOST_LINK_STATIC=ON
 [cmake.defines.os=freebsd]
 LIBDWARF_FOUND=NO
 
+# When folly is built with Homebrew LLVM clang on macOS (used by the
+# wheels CI to pick up C++23 features that AppleClang doesn't have),
+# CMake otherwise picks up Homebrew's llvm-ar, which writes BSD-style
+# archives with a "/" symbol-table member that Apple's classic linker
+# cannot parse for empty archives. Several folly portability libraries
+# have no source files on darwin and so produce exactly such empty
+# archives, which then fail to link. Forcing Apple's /usr/bin/ar and
+# /usr/bin/ranlib avoids this -- they write archives the system linker
+# always accepts. AppleClang already uses /usr/bin/ar by default, so
+# this is a no-op for AppleClang folly users.
+[cmake.defines.os=darwin]
+CMAKE_AR=/usr/bin/ar
+CMAKE_RANLIB=/usr/bin/ranlib
+
 [cmake.defines.test=on]
 BUILD_TESTS=ON
 BUILD_BENCHMARKS=OFF