Combine --gcc-toolchain and -gcc-install-dir tests.

Also fix -help output checks.

Author: Meinersbur

flang/test/Driver/driver-help-hidden.f90

@@ -104,6 +104,9 @@
 ! CHECK-NEXT: -fversion-loops-for-stride
 ! CHECK-NEXT:                         Create unit-strided versions of loops
 ! CHECK-NEXT: -fxor-operator          Enable .XOR. as a synonym of .NEQV.
+! CHECK-NEXT: --gcc-install-dir=<value>
+! CHECK-NEXT:                         Use GCC installation in the specified directory. The directory ends with path components like 'lib{,32,64}/gcc{,-cross}/$triple/$version'. Note: executables (e.g. ld) used by the compiler are not overridden by the selected GCC installation
+! CHECK-NEXT: --gcc-toolchain=<value> Specify a directory where Clang can find 'include' and 'lib{,32,64}/gcc{,-cross}/$triple/$version'. Clang will use the GCC installation with the largest version
 ! CHECK-NEXT: -gline-directives-only  Emit debug line info directives only
 ! CHECK-NEXT: -gline-tables-only      Emit debug line number tables only
 ! CHECK-NEXT: -gpulibc                Link the LLVM C Library for GPUs

flang/test/Driver/driver-help.f90

@@ -92,6 +92,9 @@
 ! HELP-NEXT: -fversion-loops-for-stride
 ! HELP-NEXT:                         Create unit-strided versions of loops
 ! HELP-NEXT: -fxor-operator          Enable .XOR. as a synonym of .NEQV.
+! HELP-NEXT: --gcc-install-dir=<value>
+! HELP-NEXT:                         Use GCC installation in the specified directory. The directory ends with path components like 'lib{,32,64}/gcc{,-cross}/$triple/$version'. Note: executables (e.g. ld) used by the compiler are not overridden by the selected GCC installation
+! HELP-NEXT: --gcc-toolchain=<value> Specify a directory where Clang can find 'include' and 'lib{,32,64}/gcc{,-cross}/$triple/$version'. Clang will use the GCC installation with the largest version
 ! HELP-NEXT: -gline-directives-only  Emit debug line info directives only
 ! HELP-NEXT: -gline-tables-only      Emit debug line number tables only
 ! HELP-NEXT: -gpulibc                Link the LLVM C Library for GPUs

flang/test/Driver/gcc-install-dir.f90

@@ -0,0 +1,18 @@
+!! Test that --gcc-toolchain and --gcc-install-dir options are working as expected.
+!! It does not test cross-compiling (--sysroot), so crtbegin.o, libgcc/compiler-rt, libc, libFortranRuntime, etc. are not supposed to be affected.
+
+! RUN: %flang 2>&1 -### -o %t %s -no-integrated-as -fuse-ld=ld --target=i386-unknown-linux-gnu --gcc-toolchain=%S/Inputs/basic_cross_linux_tree/usr                                         | FileCheck %s --check-prefix=CHECK-I386
+! RUN: %flang 2>&1 -### -o %t %s -no-integrated-as -fuse-ld=ld --target=i386-unknown-linux-gnu --gcc-install-dir=%S/Inputs/basic_cross_linux_tree/usr/lib/gcc/i386-unknown-linux-gnu/10.2.0 | FileCheck %s --check-prefix=CHECK-I386
+! CHECK-I386:      "-fc1" "-triple" "i386-unknown-linux-gnu" 
+! CHECK-I386:      "[[PREFIX:[^"]+]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/i386-unknown-linux-gnu/10.2.0/../../../../i386-unknown-linux-gnu/bin{{/|\\\\}}as"
+! CHECK-I386:      "[[PREFIX]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/i386-unknown-linux-gnu/10.2.0/../../../../i386-unknown-linux-gnu/bin{{/|\\\\}}ld" {{.*}} "-m" "elf_i386"
+! CHECK-I386-SAME: "-L[[PREFIX]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/i386-unknown-linux-gnu/10.2.0" 
+! CHECK-I386-SAME: "-L[[PREFIX]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/i386-unknown-linux-gnu/10.2.0/../../../../i386-unknown-linux-gnu/lib"
+
+! RUN: %flang 2>&1 -### -o %t %s -no-integrated-as -fuse-ld=ld --target=x86_64-unknown-linux-gnu --gcc-toolchain=%S/Inputs/basic_cross_linux_tree/usr                                           | FileCheck %s --check-prefix=CHECK-X86-64
+! RUN: %flang 2>&1 -### -o %t %s -no-integrated-as -fuse-ld=ld --target=x86_64-unknown-linux-gnu --gcc-install-dir=%S/Inputs/basic_cross_linux_tree/usr/lib/gcc/x86_64-unknown-linux-gnu/10.2.0 | FileCheck %s --check-prefix=CHECK-X86-64
+! CHECK-X86-64:      "-fc1" "-triple" "x86_64-unknown-linux-gnu"
+! CHECK-X86-64:      "[[PREFIX:[^"]+]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/x86_64-unknown-linux-gnu/10.2.0/../../../../x86_64-unknown-linux-gnu/bin{{/|\\\\}}as" "--64"
+! CHECK-X86-64:      "[[PREFIX]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/x86_64-unknown-linux-gnu/10.2.0/../../../../x86_64-unknown-linux-gnu/bin{{/|\\\\}}ld" {{.*}} "-m" "elf_x86_64"
+! CHECK-X86-64-SAME: "-L[[PREFIX]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/x86_64-unknown-linux-gnu/10.2.0" 
+! CHECK-X86-64-SAME: "-L[[PREFIX]]/Inputs/basic_cross_linux_tree/usr/lib/gcc/x86_64-unknown-linux-gnu/10.2.0/../../../../x86_64-unknown-linux-gnu/lib"