[flang][driver] Add missing dependency in unit tests (nfc)

The following patch revealed a missing dependency in the CMake script
for Flang driver unit tests:
  * https://reviews.llvm.org/D96032
The following buildbots are failing ("BUILD_SHARED_LIBS" is set to ON):
  * http://lab.llvm.org:8011/#/builders/134/builds/1840
  * http://lab.llvm.org:8011/#/builders/66/builds/1785
  * http://lab.llvm.org:8011/#/builders/33/builds/2436

This patch adds the missing dependency.

From what I can see, FortranSemantics and FortranParser are only
indirect dependencies of FlangFrontendTests and IIUC shouldn't be
required here. This is something that we should revisit at some point.
In this patch I focus on fixing the build.

GitOrigin-RevId: cf471632b1bd02d6f6e582c8c0f82043f7d09946
diff --git a/unittests/Frontend/CMakeLists.txt b/unittests/Frontend/CMakeLists.txt
index 7b507b3..88ec86f 100644
--- a/unittests/Frontend/CMakeLists.txt
+++ b/unittests/Frontend/CMakeLists.txt
@@ -9,4 +9,5 @@
   flangFrontend
   flangFrontendTool
   FortranParser
+  FortranSemantics
 )