[libc] fix locale dependency for stdlib (#108042)

Address the following issue:
```
❯ ninja libc.test.src.__support.OSUtil.linux.vdso_test.__unit__
[91/127] Building CXX object libc/test/src/__support/OSUtil/linux/CMakeFiles/libc.test.src.__support.OSUtil.linux.vdso_test.__unit__.__build__.dir/vdso_test.cpp.o
FAILED: libc/test/src/__support/OSUtil/linux/CMakeFiles/libc.test.src.__support.OSUtil.linux.vdso_test.__unit__.__build__.dir/vdso_test.cpp.o 
sccache /usr/bin/clang++ -DLIBC_NAMESPACE=__llvm_libc_20_0_0_git -D_DEBUG -I/home/schrodingerzy/Documents/llvm-project/libc -isystem /home/schrodingerzy/Documents/llvm-project/build/libc/include -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -g -std=gnu++17 -fpie -DLIBC_FULL_BUILD -ffreestanding -fno-exceptions -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-rtti -MD -MT libc/test/src/__support/OSUtil/linux/CMakeFiles/libc.test.src.__support.OSUtil.linux.vdso_test.__unit__.__build__.dir/vdso_test.cpp.o -MF libc/test/src/__support/OSUtil/linux/CMakeFiles/libc.test.src.__support.OSUtil.linux.vdso_test.__unit__.__build__.dir/vdso_test.cpp.o.d -o libc/test/src/__support/OSUtil/linux/CMakeFiles/libc.test.src.__support.OSUtil.linux.vdso_test.__unit__.__build__.dir/vdso_test.cpp.o -c /home/schrodingerzy/Documents/llvm-project/libc/test/src/__support/OSUtil/linux/vdso_test.cpp
In file included from /home/schrodingerzy/Documents/llvm-project/libc/test/src/__support/OSUtil/linux/vdso_test.cpp:21:
In file included from /home/schrodingerzy/Documents/llvm-project/libc/test/UnitTest/ErrnoSetterMatcher.h:13:
In file included from /home/schrodingerzy/Documents/llvm-project/libc/src/__support/FPUtil/fpbits_str.h:12:
In file included from /home/schrodingerzy/Documents/llvm-project/libc/src/__support/CPP/string.h:20:
/home/schrodingerzy/Documents/llvm-project/build/libc/include/stdlib.h:13:10: fatal error: 'llvm-libc-types/locale_t.h' file not found
   13 | #include "llvm-libc-types/locale_t.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
[123/127] Building CXX object libc/test/UnitTest/CMakeFiles/LibcTest.unit.dir/LibcTestMain.cpp.o
ninja: build stopped: subcommand failed.
```

Author: SchrodingerZhu

libc/include/CMakeLists.txt

@@ -347,6 +347,7 @@ add_header_macro(
     .llvm-libc-types.__qsortcompare_t
     .llvm-libc-types.__qsortrcompare_t
     .llvm-libc-types.__atexithandler_t
+    .llvm-libc-types.locale_t
 )
 
 add_header_macro(