build(deps): Account for header changes in fmt project trunk (#4109)

Fixes a CI breakage

Signed-off-by: Larry Gritz <[email protected]>

Author: lgritz

src/cmake/externalpackages.cmake

@@ -350,7 +350,11 @@ macro (find_or_download_fmt)
         endif ()
         set (FMT_INCLUDE_DIR "${FMT_INSTALL_DIR}/include")
         set (OIIO_USING_FMT_LOCAL TRUE)
-        file (STRINGS "${FMT_INCLUDE_DIR}/fmt/core.h" TMP REGEX "^#define FMT_VERSION .*$")
+        if (EXISTS "${FMT_INCLUDE_DIR}/fmt/base.h")
+            file (STRINGS "${FMT_INCLUDE_DIR}/fmt/base.h" TMP REGEX "^#define FMT_VERSION .*$")
+        else ()
+            file (STRINGS "${FMT_INCLUDE_DIR}/fmt/core.h" TMP REGEX "^#define FMT_VERSION .*$")
+        endif ()
         string (REGEX MATCHALL "[0-9]+" FMT_VERSION_NUMERIC ${TMP})
         math(EXPR FMT_VERSION_PATCH "${FMT_VERSION_NUMERIC} % 100")
         math(EXPR FMT_VERSION_MINOR "(${FMT_VERSION_NUMERIC} / 100) % 100")

src/include/CMakeLists.txt

@@ -69,6 +69,9 @@ if (INTERNALIZE_FMT OR OIIO_USING_FMT_LOCAL)
     if (fmt_VERSION VERSION_GREATER_EQUAL 9)
         list (APPEND fmt_headers_base_names std.h)
     endif ()
+    if (EXISTS "${FMT_INCLUDE_DIR}/fmt/base.h")
+        list (APPEND fmt_headers_base_names base.h)
+    endif ()
     set (fmt_internal_directory ${CMAKE_BINARY_DIR}/include/OpenImageIO/detail/fmt)
     list (TRANSFORM fmt_headers_base_names
           PREPEND ${FMT_INCLUDE_DIR}/fmt/