Fix build type, support offline builds

- Quote -DCMAKE_BUILD_TYPE arg in build script to fix PowerShell
  parameter parsing (was passing literal '\' instead of
  the resolved value, resulting in unoptimized 4MB .so on Linux)
- Allow pre-installed Firebird headers via -DFIREBIRD_INCLUDE_DIR=path,
  skipping FetchContent download (enables air-gapped builds)
- Use find_package(GTest) first, fall back to FetchContent only when
  not found (enables builds without internet access)

Author: fdcastel

cmake/FetchFirebirdHeaders.cmake

@@ -8,10 +8,25 @@
 # (ibase.h, iberror.h) and the firebird/ sub-tree with the modern API
 # (Interface.h, IdlFbInterfaces.h, Message.h, impl/, …).
 #
+# To use pre-installed headers (e.g. on an air-gapped host), set
+# FIREBIRD_INCLUDE_DIR on the command line:
+#   cmake -B build -DFIREBIRD_INCLUDE_DIR=/path/to/firebird/include
+#
 # Usage:
 #   include(cmake/FetchFirebirdHeaders.cmake)
 #   target_include_directories(MyTarget PRIVATE ${FIREBIRD_INCLUDE_DIR})
 
+# If the caller already provided FIREBIRD_INCLUDE_DIR, validate and skip fetch.
+if(FIREBIRD_INCLUDE_DIR)
+    if(NOT EXISTS "${FIREBIRD_INCLUDE_DIR}/ibase.h")
+        message(FATAL_ERROR
+            "FIREBIRD_INCLUDE_DIR is set to '${FIREBIRD_INCLUDE_DIR}' "
+            "but ibase.h was not found there.")
+    endif()
+    message(STATUS "Firebird headers (pre-installed): ${FIREBIRD_INCLUDE_DIR}")
+    return()
+endif()
+
 include(FetchContent)
 
 # Pin to Firebird 5.0.2 – bump when upgrading the target engine version.

firebird-odbc-driver.build.ps1

@@ -42,7 +42,7 @@ task clean {
 
 # Synopsis: Build the driver and tests (default task).
 task build {
-	exec { cmake -B $BuildDir -S $BuildRoot -DCMAKE_BUILD_TYPE=$Configuration -DBUILD_TESTING=ON }
+	exec { cmake -B $BuildDir -S $BuildRoot "-DCMAKE_BUILD_TYPE=$Configuration" -DBUILD_TESTING=ON }
 
 	if ($IsWindowsOS) {
 		exec { cmake --build $BuildDir --config $Configuration }

tests/CMakeLists.txt

@@ -19,22 +19,28 @@ if(NOT CMAKE_PROJECT_NAME OR CMAKE_PROJECT_NAME STREQUAL "FirebirdOdbcTests")
 endif()
 
 # ---------------------------------------------------------------------------
-# Google Test — prefer FetchContent (integrated build), fall back to find_package
+# Google Test — prefer find_package (pre-installed), fall back to FetchContent
 # ---------------------------------------------------------------------------
-include(FetchContent)
-FetchContent_Declare(
-    googletest
-    URL https://github.com/google/googletest/archive/refs/tags/v1.14.0.zip
-    DOWNLOAD_EXTRACT_TIMESTAMP TRUE
-)
-# Prevent GTest from overriding parent project settings
-set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
-set(INSTALL_GTEST OFF CACHE BOOL "" FORCE)
-# Build GTest as a static library (the test exe doesn't need a separate DLL)
-set(BUILD_SHARED_LIBS_SAVED ${BUILD_SHARED_LIBS})
-set(BUILD_SHARED_LIBS OFF)
-FetchContent_MakeAvailable(googletest)
-set(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_SAVED})
+find_package(GTest CONFIG QUIET)
+if(GTest_FOUND)
+    message(STATUS "Google Test: using pre-installed (find_package)")
+else()
+    message(STATUS "Google Test: not found locally, fetching via FetchContent")
+    include(FetchContent)
+    FetchContent_Declare(
+        googletest
+        URL https://github.com/google/googletest/archive/refs/tags/v1.14.0.zip
+        DOWNLOAD_EXTRACT_TIMESTAMP TRUE
+    )
+    # Prevent GTest from overriding parent project settings
+    set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+    set(INSTALL_GTEST OFF CACHE BOOL "" FORCE)
+    # Build GTest as a static library (the test exe doesn't need a separate DLL)
+    set(BUILD_SHARED_LIBS_SAVED ${BUILD_SHARED_LIBS})
+    set(BUILD_SHARED_LIBS OFF)
+    FetchContent_MakeAvailable(googletest)
+    set(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_SAVED})
+endif()
 
 # ---------------------------------------------------------------------------
 # Find ODBC
@@ -98,7 +104,11 @@ add_executable(firebird_odbc_tests
 # ---------------------------------------------------------------------------
 # Link against Google Test and the ODBC Driver Manager
 # ---------------------------------------------------------------------------
-target_link_libraries(firebird_odbc_tests PRIVATE gtest ODBC::ODBC)
+if(GTest_FOUND)
+    target_link_libraries(firebird_odbc_tests PRIVATE GTest::gtest ODBC::ODBC)
+else()
+    target_link_libraries(firebird_odbc_tests PRIVATE gtest ODBC::ODBC)
+endif()
 
 # ---------------------------------------------------------------------------
 # Discover tests for CTest