Fix allocations and compiler warnings in ZROTG (#4289) #589

Job	Run time
build (ubuntu-latest, gfortran, cmake)	12m 59s
build (ubuntu-latest, gfortran, make)	8m 51s
build (ubuntu-latest, flang, cmake)	25m 45s
build (ubuntu-latest, flang, make)	8m 44s
build (macos-latest, gfortran, cmake)	1h 2m 56s
build (macos-latest, gfortran, make)	20m 41s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	5m 4s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	10m 39s
msys2 (UCRT64, int32, Release)	21m 57s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	6m 19s
msys2 (UCRT64, int64, Release)	13m 39s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 40s
msys2 (MINGW32, int32, Release)	28m 46s
msys2 (CLANG64, int32, Release)	18m 59s
msys2 (CLANG64, int64, Release)	34m 55s
msys2 (CLANG32, int32, Release)	16m 19s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	12m 56s
	5h 12m 9s

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