Export of internal Abseil changes

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a1b28d83d60f96e14487f093566f12ba07f92732 by Mark Barolak <mbar@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 342270204

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3d99c08b7e2ee23050f64965f09881b54821cdd0 by Mark Barolak <mbar@google.com>:

Fix a Windows DLL breakage that is causing all sub-libraries to be compiled as DLL dependencies instead of stand-alone DLLs.

See https://github.com/abseil/abseil-cpp/issues/796 for the bug report.

Import of https://github.com/abseil/abseil-cpp/pull/797

PiperOrigin-RevId: 341892182
GitOrigin-RevId: a1b28d83d60f96e14487f093566f12ba07f92732
Change-Id: I7d70f07492bfa9b657ec280a4f005c1ee893594c

CMake/AbseilHelpers.cmake

@@ -122,7 +122,11 @@ function(absl_cc_library)
   # 4. "static"  -- This target does not depend on the DLL and should be built
   #                 statically.
   if (${ABSL_BUILD_DLL})
+    if(ABSL_ENABLE_INSTALL)
       absl_internal_dll_contains(TARGET ${_NAME} OUTPUT _in_dll)
+    else()
+      absl_internal_dll_contains(TARGET ${ABSL_CC_LIB_NAME} OUTPUT _in_dll)
+    endif()
     if (${_in_dll})
       # This target should be replaced by the DLL
       set(_build_type "dll")

absl/time/internal/cctz/src/time_zone_libc.cc

@@ -27,6 +27,12 @@
 #include "absl/time/internal/cctz/include/cctz/civil_time.h"
 #include "absl/time/internal/cctz/include/cctz/time_zone.h"
 
+#if defined(_AIX)
+extern "C" {
+extern long altzone;
+}
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace time_internal {
@@ -44,7 +50,7 @@ auto tm_zone(const std::tm& tm) -> decltype(_tzname[0]) {
   const bool is_dst = tm.tm_isdst > 0;
   return _tzname[is_dst];
 }
-#elif defined(__sun)
+#elif defined(__sun) || defined(_AIX)
 // Uses the globals: 'timezone', 'altzone' and 'tzname'.
 auto tm_gmtoff(const std::tm& tm) -> decltype(timezone) {
   const bool is_dst = tm.tm_isdst > 0;

absl/time/internal/cctz/src/tzfile.h

@@ -112,7 +112,7 @@ struct tzhead {
 
 #ifndef TZ_MAX_CHARS
 #define TZ_MAX_CHARS 50 /* Maximum number of abbreviation characters */
-/* (limited by what unsigned chars can hold) */
+                        /* (limited by what unsigned chars can hold) */
 #endif                  /* !defined TZ_MAX_CHARS */
 
 #ifndef TZ_MAX_LEAPS