Move generation of SPIRV-Cross/mvkSpirvCrossRevisionDerived.h to separate script.

Add Scripts/gen_spirv_cross_rev_hdr.sh script and
call from ExternalDependencies SPIRV-Cross build.
diff --git a/ExternalDependencies.xcodeproj/project.pbxproj b/ExternalDependencies.xcodeproj/project.pbxproj
index 9827d91..e3b2b57 100644
--- a/ExternalDependencies.xcodeproj/project.pbxproj
+++ b/ExternalDependencies.xcodeproj/project.pbxproj
@@ -1108,6 +1108,7 @@
 		450A4F64221C5A95007203D7 /* spirv_reflect.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = spirv_reflect.cpp; sourceTree = "<group>"; };
 		A90FD89F21CC4EAB00B92BB2 /* libSPIRVCross.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libSPIRVCross.a; sourceTree = BUILT_PRODUCTS_DIR; };
 		A90FD9E421CC4EB900B92BB2 /* libSPIRVCross.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libSPIRVCross.a; sourceTree = BUILT_PRODUCTS_DIR; };
+		A91BF011235F9C510039B7DE /* gen_spirv_cross_rev_hdr.sh */ = {isa = PBXFileReference; lastKnownFileType = text.script.sh; path = gen_spirv_cross_rev_hdr.sh; sourceTree = "<group>"; };
 		A9679AAC21D269D900856BF7 /* package_ext_libs_macos.sh */ = {isa = PBXFileReference; lastKnownFileType = text.script.sh; path = package_ext_libs_macos.sh; sourceTree = "<group>"; };
 		A9679AAD21D269D900856BF7 /* package_ext_libs_ios.sh */ = {isa = PBXFileReference; lastKnownFileType = text.script.sh; path = package_ext_libs_ios.sh; sourceTree = "<group>"; };
 		A9679AAE21D269D900856BF7 /* package_ext_libs.sh */ = {isa = PBXFileReference; lastKnownFileType = text.script.sh; path = package_ext_libs.sh; sourceTree = "<group>"; };
@@ -1642,6 +1643,7 @@
 		A9679AAB21D2699800856BF7 /* Scripts */ = {
 			isa = PBXGroup;
 			children = (
+				A91BF011235F9C510039B7DE /* gen_spirv_cross_rev_hdr.sh */,
 				A9679AAD21D269D900856BF7 /* package_ext_libs_ios.sh */,
 				A9679AAC21D269D900856BF7 /* package_ext_libs_macos.sh */,
 				A9679AAE21D269D900856BF7 /* package_ext_libs.sh */,
@@ -2880,6 +2882,7 @@
 			buildPhases = (
 				A976290021CC608E00B52A68 /* Headers */,
 				A976290121CC609100B52A68 /* Sources */,
+				A91BF013235F9EED0039B7DE /* Generate Revision Header */,
 			);
 			buildRules = (
 			);
@@ -2896,6 +2899,7 @@
 			buildPhases = (
 				A97628FF21CC608900B52A68 /* Headers */,
 				A97628FE21CC608400B52A68 /* Sources */,
+				A91BF012235F9E220039B7DE /* Generate Revision Header */,
 			);
 			buildRules = (
 			);
@@ -3018,6 +3022,42 @@
 /* End PBXProject section */
 
 /* Begin PBXShellScriptBuildPhase section */
+		A91BF012235F9E220039B7DE /* Generate Revision Header */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			inputPaths = (
+			);
+			name = "Generate Revision Header";
+			outputFileListPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "\"${SRCROOT}/Scripts/gen_spirv_cross_rev_hdr.sh\"\n";
+		};
+		A91BF013235F9EED0039B7DE /* Generate Revision Header */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			inputPaths = (
+			);
+			name = "Generate Revision Header";
+			outputFileListPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "\"${SRCROOT}/Scripts/gen_spirv_cross_rev_hdr.sh\"\n";
+		};
 		A9679AAF21D26C1400856BF7 /* Package External Libraries */ = {
 			isa = PBXShellScriptBuildPhase;
 			buildActionMask = 2147483647;
diff --git a/Scripts/gen_spirv_cross_rev_hdr.sh b/Scripts/gen_spirv_cross_rev_hdr.sh
new file mode 100755
index 0000000..d4311a6
--- /dev/null
+++ b/Scripts/gen_spirv_cross_rev_hdr.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+
+# Record the SPIRV-Cross revision as a derived header file suitable for including in a build
+EXT_DIR="${SRCROOT}/External"
+EXT_REV_DIR="${SRCROOT}/ExternalRevisions"
+REPO_NAME=SPIRV-Cross
+REPO_REV=$(cat "${EXT_REV_DIR}/${REPO_NAME}_repo_revision")
+HDR_FILE=${EXT_DIR}/${REPO_NAME}/mvkSpirvCrossRevisionDerived.h
+echo "// Auto-generated by MoltenVK" > ${HDR_FILE}
+echo "static const char* spirvCrossRevisionString = \"${REPO_REV}\";" >> ${HDR_FILE}
+
diff --git a/fetchDependencies b/fetchDependencies
index 89ad70e..08ce79e 100755
--- a/fetchDependencies
+++ b/fetchDependencies
@@ -197,10 +197,6 @@
 	update_repo ${REPO_NAME} ${REPO_URL} ${REPO_REV}
 fi
 
-# Record the SPIRV-Cross revision as a derived header file suitable for including in a build
-HDR_FILE=${REPO_NAME}/mvkSpirvCrossRevisionDerived.h
-echo "// Auto-generated by MoltenVK" > ${HDR_FILE}
-echo "static const char* spirvCrossRevisionString = \"${REPO_REV}\";" >> ${HDR_FILE}
 
 
 # ----------------- glslang -------------------