boost: revision bump to migrate to icu4c@75

Formula/b/boost.rb

@@ -2,6 +2,7 @@ class Boost < Formula
   desc "Collection of portable C++ source libraries"
   homepage "https://www.boost.org/"
   license "BSL-1.0"
+  revision 1
   head "https://github.com/boostorg/boost.git", branch: "master"
 
   stable do
@@ -41,7 +42,7 @@ class Boost < Formula
     sha256 cellar: :any_skip_relocation, x86_64_linux:   "9b54de744fca5203371e41bbe08f18fe347d9873558b9b0e1c40b60e4bc5515c"
   end
 
-  depends_on "icu4c"
+  depends_on "icu4c@75"
   depends_on "xz"
   depends_on "zstd"
 
@@ -59,11 +60,11 @@ def install
     end
 
     # libdir should be set by --prefix but isn't
-    icu4c_prefix = Formula["icu4c"].opt_prefix
+    icu4c = deps.map(&:to_formula).find { |f| f.name.match?(/^icu4c@\d+$/) }
     bootstrap_args = %W[
       --prefix=#{prefix}
       --libdir=#{lib}
-      --with-icu=#{icu4c_prefix}
+      --with-icu=#{icu4c.opt_prefix}
     ]
 
     # Handle libraries that will not be built.
@@ -88,9 +89,10 @@ def install
       link=shared,static
     ]
 
-    # Boost is using "clang++ -x c" to select C compiler which breaks C++14
-    # handling using ENV.cxx14. Using "cxxflags" and "linkflags" still works.
-    args << "cxxflags=-std=c++14"
+    # Boost is using "clang++ -x c" to select C compiler which breaks C++
+    # handling in superenv. Using "cxxflags" and "linkflags" still works.
+    # C++17 is due to `icu4c`.
+    args << "cxxflags=-std=c++17"
     args << "cxxflags=-stdlib=libc++" << "linkflags=-stdlib=libc++" if ENV.compiler == :clang
 
     system "./bootstrap.sh", *bootstrap_args